Question

若(x+3)(x+m)=x^2+kx-15,则k+m的值为(?) A.-3 B.5 C.-2 D.2

Answer 1

(x+3)(x+m)=x^2+kx-15

x^2+(m+3)x+3m=x^2+kx-15

对应相等

m+3=k

3m=-15

解得

m=-5

k=-2

m+k=-7

哪个都选不了.