Nanchong Xichong County 2008-2009 junior high school mathematics final test questions (including answers)

Nanchong Xichong County 2008-2009 junior high school mathematics final test questions (including answers)

Grade 7 mathematics final examination question 1 / multiple choice question (30 points, 6 points for each question) x051. It is known that a = 3, B = 4, C = 5 has () (a) a

If (x + 3) (x + m) = x ^ 2 + kx-15, then K + M = ()
(A)-3 (B)5 (C)-2 (D)2

Correspondence coefficient method
(x+3)(x+m)=x^2+（3+m）x+3m=x^2+kx-15
So 3 + M = K and 3M = - 15
So m = - 5, k = - 2
k+m=-7
There is no answer

If (x + 3) (x + m) = x2-kx-15, then the values of K + m are a, - 3b, 5C, - 2D, 2

(x+3)(x+m)
=x²+(m+3)x+3m
=x²-kx-15
So m + 3 = - K
3m=-15
m=-5
k=-(m+3)=2
k+m=-3
Choose a