Question

在有理数范围内,下列多项式能用公式法进行因式分解的是

Answer 1

选C：

a^2 - ab - (b^2)/4

=a^2 - ab/2 - ab/2- (b^2)/4

=a(a - b/2) -(b/2)(a - b/2)

=(a - b/2)*(a - b/2)

=(a- b/2)^2

反推：

(a- b/2)^2

=a^2 - 2*a*(b/2) +(b/2)^2

=a的平方 - ab + 四分之一b的平方