1.计算 (1) (5x-2y)^2+20xy (2)(x-3)^2(x+3)^2 (3) (3x-5)^2-(2x+7)^2 (4)(x+y+1)1.计算 (1) (5x-2y)^2+20xy (2)(x-3)^2(x+3)^2 (3) (3x-5)^2-(2x+7)^2 (4)(x+y+1)(x+y-1)(5)89.8^2 (6)47^2-94×27+27^2
问题描述:
1.计算 (1) (5x-2y)^2+20xy (2)(x-3)^2(x+3)^2 (3) (3x-5)^2-(2x+7)^2 (4)(x+y+1)
1.计算 (1) (5x-2y)^2+20xy (2)(x-3)^2(x+3)^2
(3) (3x-5)^2-(2x+7)^2 (4)(x+y+1)(x+y-1)
(5)89.8^2 (6)47^2-94×27+27^2
答
(1)25x^2+4y^2
(2)(x-3)^2(x+3)^2
(3)5x^2-58x-24
(4)x^2+y^2+2xy-1
(5)………………
(6)………………
答
1.计算 (1) (5x-2y)^2+20xy =25x^2-20xy+4y^2+20xy=25x^2+4y^2(2)(x-3)^2(x+3)^2 =(x^2-9)^2=x^4-18x^2+81(3) (3x-5)^2-(2x+7)^2=(3x-5+2x+7)(3x-5-2x-7)=(5x-2)(x-12)=5x^2-60x-2x+24=5x^2-62x+2...