初一下平方差公式计算(过程详细)

发布网友 发布时间：2022-06-04 23:34

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热心网友 时间：2022-07-09 09:35

(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)(-1/4x+2y)
=(-1/4x)^2-(2y)^2
=1/16x^2-4y^2
(6).x^2+(y-x)(y+x)
=x^2+(y^2-x^2)
=y^2
(7).(a^n+b)(a^n-b)
=(a^n)^2-b^2
=a^2n-n^2
(8).(a+1)(a-1)(a^2+1)
=(a^2-1)(a^2+1)
=a^4-1

热心网友 时间：2022-07-09 09:35

解：(1).(3x+7y)(3x-7y)=9x^2-49y^2
(2).(0.2x-0.3)(0.2x+0.3)= 0.04x^2-0.09
(3).(mn-3n)(mn+3n)=(mn)^2-9n^2
(4).(-2x+3y)(-2x-3y)=4x^2-9y^2
(5).(-1/4x-2y)(-1/4x+2y)=1/16x^(-2)-4y^2
(6).x^2+(y-x)(y+x)=y^2
(7).(a^n+b)(a^n-b)=a^2n-b^2
(8).(a+1)(a-1)(a^2+1)=a^4-1
以上均利用平方差公式a^2-b^2=(a+b)(a-b);

热心网友 时间：2022-07-09 09:36

(1).(3x+7y)(3x-7y)
=9x^2-49y^2;

(2).(0.2x-0.3)(0.2x+0.3)
=0.04x^2-0.09;

(3).(mn-3n)(mn+3n)
=m^2n^2-9n^2;

(4).(-2x+3y)(-2x-3y)
=4x^2-9y^2;

(5).(-1/4x-2y)(-1/4x+2y)
=x^2/16-4y^2;

(6).x^2+(y-x)(y+x)
=x^2+y^2-x^2
=y^2;

(7).(a^n+b)(a^n-b)
=(a^n)^2-b^2
=a^(2n)-b^2;

(8).(a+1)(a-1)(a^2+1)
=(a^2-1)(a^2+1)
=a^4-1.

热心网友 时间：2022-07-09 09:36

(1).(3x+7y)(3x-7y)
=9x^2-49y^2

(2).(0.2x-0.3)(0.2x+0.3)
=0.04x^2-0.09

(3).(mn-3n)(mn+3n)
=m^2n^2-9n^2

(4).(-2x+3y)(-2x-3y)
=4x^2-9y^2

(5).(-1/4x-2y)(-1/4x+2y)
=1/16x^2-4y^2

(6).x^2+(y-x)(y+x)
=x^2-y^2+x^2
=2x^2-y^2

(7).(a^n+b)(a^n-b)
=a^(2n)-b^2

(8).(a+1)(a-1)(a^2+1)
=(a^2-1)(a^2+1)
=a^4-1

(3x+7y)(3x-7y)
=9x^2-49y^2

热心网友 时间：2022-07-09 09:37

9x^2-49y^2\0.04x^-0.09\m^2n^2-9n^2\4x^2-9y^2\1/16x^2-4y^2\y^2\a^2n-b^2\a^4-1...这些都是用a^2-b^2=(a+b)(a-b) 这个公式啊