(9a²-12ab+5b²)-(7a²+12ab+7b²) a=1/2,b=-1/2求其值

问题描述:

(9a&sup2-12ab+5b&sup2)-(7a&sup2+12ab+7b&sup2) a=1/2,b=-1/2求其值

原式=9a²-12ab+5b²-7a²-12ab-7b²
=2a²-24ab-2b²
=1/2+6-1/2
=6