Question

要使X(XX+a)+3a-2b=XX+5x+4成立．求a

Answer 1

设x^2+5x+4=0

(x+1)(x+4)=0

x=-1或x=-4

即：x=-1或x=-4时,X(XX+a)+3a-2b＝0

x=-1:-1(1+a)+3a-2b=2a-2b-1=0

x=-4:-4(16+a)+3a-2b=-a-2b-64=0

解方程组得：

a=-21