计算:7ab-{3a^2b^2+7-2[8ab^2+3a^2b^2-1/2(3+7ab)]}
问题描述:
计算:7ab-{3a^2b^2+7-2[8ab^2+3a^2b^2-1/2(3+7ab)]}
答
=7ab-(3a^2b^2+7-2(8ab^2+3a^2b^2-3/2-7/2ab)
=7ab-(3a^2b^2+7-16ab^2-6a^2b^2+3+7ab)
=7ab-3a^2b^2-10+16ab^2+6a^2b^2-7ab
=3a^2b^2+16ab^2-10若a=1/2,b=4,这个代数式的值为?若a=1/2,b=4,此代数式的值为?