Question

我太笨了,数学题几道不会,最好讲解

Answer 1

1.(a-b)²=(a+b)²-4ab=9-4×2=1

2.(3m+2)²(3m-2)²=((3m+2)(3m-2))²=(9m²-4)²

3.x²+y²=(x+y)²-2xy=1+4=5

4.a²+b²=（(a+b)²+(a-b)²）/2=（7+3）/2=5

5.(a+b)²=(a-b)²+4ab=4+4=8

6.(2m-3n)²-( )=(2m+3n)² ( )=4×2m×3n=24mn

7.((x+y)²×(x-y)²-(x²-y²)²)=4x²y²+2x²y²=6x²y²

详细思路就全都是把完全平方都拆了..

不难的,不要埋怨自己笨.多做做就会了