第三题: DS:is |x+5|=10? (1)|x-5|=10 (2)|x|-5=10 答案应该是A, V2 的答案C肯定是错误的。 具体可参看陈向东高分数学突破第21页得例20. -- by 会员 helenlife (2011/8/18 6:06:13)
I think V2 is C. Since lx-5l=10 could have two outcomes, 15 or -5, lx+5l could have two possible answers: 20 or 0. A is not sufficient. From (2),we could get x=15 or x=-15, also not sufficient for lx+5l since there will be two possible answers. By combining (1)and (2), we can lock X=15, thus it is sufficient for lx+5l , c is the right choice.
You mentioned CXD, could copy and paste the explanation you thought is related to this Q? Coz I could find it.Thanks. |