Question

已知a-b=-3,ab=1/2,求:(ab+a-b)(ab-a+b)的值

用平方差公式计算

Answer 1

(ab+a-b)(ab-a+b)
= [ab + (a - b)] [ab - (a - b)]
= (ab)² - (a - b)²
= (1/2)² - (-3)²
= 1/4 - 9
= -35/4

Answer 2

(ab+a-b)(ab-a+b)
=[ab+(a-b)]*[ab-(a-b)]
=(ab)^2-(a-b)^2
=(1/2)^2-(-3)^2
=1/4-9
=-35/4