两道数学题(写出计算过程)1.(-5x+3/2)(-5x-1.5)2.(x+2y-3)(x-2y+3)

问题描述:

两道数学题(写出计算过程)
1.(-5x+3/2)(-5x-1.5)
2.(x+2y-3)(x-2y+3)

1,.(-5x+3/2)(-5x-1.5)
=(-5x)*(-5x)-1.5*1.5
=25x*x-2.25
2,(x+2y-3)(x-2y+3)
=x*x-(2y-3)*(2y-3)
=x*x-4y*y+12y-9
现在小学生真懒……

1.(-5x+3/2)(-5x-1.5)=(-5x)²-(3/2)²=25x²-9/4
2.(x+2y-3)(x-2y+3)=x²-(2y-3)²=x²-4y²+12y-9

这2道题主要是对平方差公式的运用表达式:(a+b)(a-b)=a^2-b^2所以:1,(-5x+3/2)(-5x-1.5)=(-5x)*(-5x)-1.5*1.5=25x*x-2.252,(x+2y-3)(x-2y+3)=(x+2y-3)(x-(2y-3))=x*x-(2y-3)*(2y-3)=x*x-4y*y+12y-9...

zhezhongti……