GWD-22-5滔滔

Q5:If b, c, and d are constants and x² + bx + c = (x+d)² for all values of x, what is the value of c? b/(2d)=c/d²
                or d=0=b=c

(1)
                d = 3 =>2c=3b， 因而C未知

(2) b = 6   =>c=3d，因而C未知

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

D. EACH statement ALONE is sufficient.

E. Statements (1) and (2) TOGETHER are NOT sufficient.

答案D,为什么觉得c,解题如灰色部分

because all values of x can satisfy the equation x^2+bx+c=(x+d)^2

the coefficient of the same order of x should be identical

thus, we have b=2d and c=d^2

we know b or d, then we can get the value of c