(3x-y)(3x+y)+y(x+y);(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)快点,
问题描述：
(3x-y)(3x+y)+y(x+y);(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)快点,
答
(3x-y)(3x+y)+y(x+y);
=9X平方-Y平方+yx+Y平方;
=9X平方+yx
(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)
=a平方-1/4b平方-( 9a平方 - 4b平方 )
=15/4b平方-8a平方
答
9x平方+xy
-8a平方+15/4b平方
答
(3x-y)(3x+y)+y(x+y)=9x²-y²+xy+y²=9x²+xy=x(9x+y)(a+1/2b)(a-1/2b)-(3a-2b)(3a+2b)=a²-b²/4-(9a²-4b²)=-8a²+15b²/4