请教NN Prep2 DS的几道题目（64，65，66，91） 欢迎讨论（特别是要考得XDJM）

fangwenting

64.       5329-!-item-!-187;#058&004211

If
                a
                <
                y
                <
                z
                <
                b,
                is
                |y
                -
                a
                |
                <
                    |y
                -
                b
                |
                ?

 

(1)
                |z
                -
                a
                |
                <
                    |z
                -
                b
                |

 

  (2)
                |y
                -
                a
                |
                <
                |z
                -
                b
                |

 

答案是D    我用画数轴解的，不晓得方法对不对，但是也得不出D，请教，还有别的方法么？

-------------------------------------------------

65.       5432-!-item-!-187;#058&004252

If
            ab
                 ≠
                     0
            and
                points
            (-a,
            b)
            and
            (-b,
            a)
            are
            in
                the
                same
                quadrant
                of
                    the
                xy-plane,
                is
                point
                (-x,
                y)
                in
                this
                same
                quadrant?

 

(1)
            xy
            >
            0

 

(2)
            ax
            >
            0

 

答案是C ， 我选的A

还有一道也是关于坐标的题，也请请教：

91.       8325-!-item-!-187;#058&006143

In
                        the
                        rectangular
                            coordinate
                        system,
                        are
                        the
                        points
                        (r,
                        s)
                        and
                        (u,
                        v)
                        equidistant
                        from
                        the
                        origin?

 

(1)
                    r
                    +
                    s
                    =
                    1

 

(2)
                    u
                    =
                    1
                    -
                    r
                    and
                    v
                    =
                    1
                    -
                    s.

答案给的C， 我不知道怎么个做法

---------------------------------------------------

66.       5486-!-item-!-187;#058&004317

If
            q
            is
            a
            positive
                integer
            less
                than
            17
            and
            r
            is
            the
            remainder
            when
                17
                is
                divided
                by
                q,
                what
                is
                    the
                value
                of
                r
                ?

 

(1)
            q
            >
            10

 

(2)
            q
            =
            2k,
            where
            k
            is
            a
            positive
            integer.

答案是B， 我选的C，请教NN。

entheticism

64.       If
                a
                <
                y
                <
                z
                <
                b,
                is
                |y
                -
                a
                |
                <
                    |y
                -
                b
                |
                ?

 (1)
                        |z
                        -
                        a
                        |
                        <
                            |z
                        -
                        b
                        |

   (2)
                        |y
                        -
                        a
                        |
                        <
                        |z
                        -
                        b
                        |

 答案是D    我用画数轴解的，不晓得方法对不对，但是也得不出D，请教，还有别的方法么？

这个题其实是把不等式翻译成语言。

我翻译下哈：

y和z在ab两点间。

y离a近，z离a远。

问y到a距离小于y到b不？

条件1

z到a小于z到b

条件2

y到a小于y到b

答案就是D

-------------------------------------------------

65.      If
            ab
                 ≠
                     0
            and
                points
            (-a,
            b)
            and
            (-b,
            a)
            are
            in
                the
                same
                quadrant
                of
                    the
                xy-plane,
                is
                point
                (-x,
                y)
                in
                this
                same
                quadrant?

 (1)
                    xy
                    >
                    0

 (2)
                    ax
                    >
                    0

 

答案是C ， 我选的A

还有一道也是关于坐标的题，也请请教：

条件讲的就是ab是同号的，这样两点才能在一个象限。

这个就是符号问题，ax必须同号才能在一个象限，xy同号才能符合第一条。

91.   In
                    the
                    rectangular
                        coordinate
                    system,
                    are
                    the
                    points
                    (r,
                    s)
                    and
                    (u,
                    v)
                    equidistant
                    from
                    the
                    origin?

 (1)
                        r
                        +
                        s
                        =
                        1

 (2)
                        u
                        =
                        1
                        -
                        r
                        and
                        v
                        =
                        1
                        -
                        s.

答案给的C， 我不知道怎么个做法

问这两点到原点距离是否相同。

这两个条件联合起来就是圆的方程。

r
                        +
                        s
                        =
                        1

u
                        =
                        1
                        -
                        r
                        and
                        v
                        =
                        1
                        -
                        s.

一推 ： u+v=1

所以自然就都在圆上了。

---------------------------------------------------

66.      If
            q
            is
            a
            positive
                integer
            less
                than
            17
            and
            r
            is
            the
            remainder
            when
                17
                is
                divided
                by
                q,
                what
                is
                    the
                value
                of
                r
                ?

 (1)
                    q
                    >
                    10

 (2)
                    q
                    =
                    2k,
                    where
                    k
                    is
                    a
                    positive
                    integer.

答案是B， 我选的C，请教NN。

我是推不出来，选E。

Simon_ni1985

66 题，条件2 就是17以内的偶数，17除任何17以内的偶数余数都是1...


91: 离原点距离相同 r^2+s^2 = u^2+v^2 接下来不知道了...

cissy_lynn

66题：

条件2)如果是q=2*k，也就是如第3楼说的仅仅只是偶数，当q=6的时候，余数是5；当q=10，余数是7；当q=12，余数是5；当q=14，余数是3；当q=16，余数是1；结果只能选E。

但是，如果条件2）是q=2^k，则q只能取2,4,8,16，那么余数都是1，所以选B。

cissy_lynn

91题：

根据条件2），(u,v)到原点的距离为sqr(u^2 + v^2)=sqr(r^2 + s^2 - 2r - 2s + 2)

结合条件1），r + s = 1，则sqr(u^2 + v^2)=sqr(r^2 + s^2 - 2 + 2)=sqr(s^2 + r^2)，即(u,v)和(r,s)到原点距离相等。所以选C。

另外，r+s=1是一条x轴和y轴截距都为1的直线，不是第2楼说的圆。（圆是r^2 + s^2 = 1）。

zjpopo

受益！

fangwenting

64.       If
                        a
                        <
                        y
                        <
                        z
                        <
                        b,
                        is
                        |y
                        -
                        a
                        |
                        <
                            |y
                        -
                        b
                        |
                        ?

 (1)
                                |z
                                -
                                a
                                |
                                <
                                    |z
                                -
                                b
                                |

 (1)
                        |z
                        -
                        a
                        |
                        <
                            |z
                        -
                        b
                        |

   (2)
                                |y
                                -
                                a
                                |
                                <
                                |z
                                -
                                b
                                |

   (2)
                        |y
                        -
                        a
                        |
                        <
                        |z
                        -
                        b
                        |

 答案是D    我用画数轴解的，不晓得方法对不对，但是也得不出D，请教，还有别的方法么？

 答案是D    我用画数轴解的，不晓得方法对不对，但是也得不出D，请教，还有别的方法么？

这个题其实是把不等式翻译成语言。

我翻译下哈：

y和z在ab两点间。

y离a近，z离a远。

问y到a距离小于y到b不？

条件1

z到a小于z到b

条件2

y到a小于y到b

答案就是D

怎么可以得出y离a近，z离a远呢，是a<y<z, 但不是|a|<|y|<|z|哦，可能是负数呢

fangwenting

91.   In
                the
                rectangular
                    coordinate
                system,
                are
                the
                points
                (r,
                s)
                and
                (u,
                v)
                equidistant
                from
                the
                origin?

 (1)
                    r
                    +
                    s
                    =
                    1

 (1)
            r
            +
            s
            =
            1

 (2)
                    u
                    =
                    1
                    -
                    r
                    and
                    v
                    =
                    1
                    -
                    s.

 (2)
            u
            =
            1
            -
            r
            and
            v
            =
            1
            -
            s.

答案给的C， 我不知道怎么个做法

问这两点到原点距离是否相同。

这两个条件联合起来就是圆的方程。

r
                    +
                    s
                    =
                    1

u
                    =
                    1
                    -
                    r
                    and
                    v
                    =
                    1
                    -
                    s.

一推 ： u+v=1

所以自然就都在圆上了。

谢谢。。。。

fangwenting

以下是引用Simon_ni1985在2009-1-14 7:25:00的发言：
66 题，条件2 就是17以内的偶数，17除任何17以内的偶数余数都是1...

    

    

谢谢，懂啦

Simon_ni1985

汗...66题 应如4楼所说