题目

初一下平方差公式计算(过程详细)
(1).(3x+7y)(3x-7y0
(2).(0.2x-0.3)(0.2x+0.3)
(3).(mn-3n)(mn+3n)
(4).(-2x+3y)(-2x-3y)
(5).(-1/4x-2y)(-1/4x+2y)
(6).x^2+(y-x)(y+x)
(7).(a^n+b)(a^n-b)
(8).(a+1)(a-1)(a^2+1)
1).(3x+7y)(3x-7y)

提问时间：2020-10-30

答案

(1).(3x+7y)(3x-7y)=(3x)^2-(7y)^2=9x^2-49y^2(2).(0.2x-0.3)(0.2x+0.3) =(0.2x)^2-0.3^2=0.04x^2-0.09(3).(mn-3n)(mn+3n) =(mn)^2-(3n)^2=m^2n^2-9n^2(4).(-2x+3y)(-2x-3y) =(-2x)^2-(3y)^2=4x^2-9y^2(5).(-1/4x-2y...