先化简,再求值(-12x^2-4xy)-2(5xy-8x^2),其中x=-1,y=0.4
问题描述:
先化简,再求值(-12x^2-4xy)-2(5xy-8x^2),其中x=-1,y=0.4
答
(-12x²-4xy)-2(5xy-8x²)
=-12x²-4xy-10xy+16x²
=4x²-14xy
=4×(-1)²-14×(-1)×0.4
=4+5.6
=9.6