以下五道因式分解哪些是错的?怎样改正?1.4(x-y)^2-9(x+y)^2=2^2(x-y)^2-3^2(x+y)^2=(2+3)(2-3)[(x-y)+(x+y)]*[(x-y)-(x+y)]=5*(-1)*2x*(-2y)=20xy2.a^2-4-a+2=(a+2)(a-2)-(a+2)=(a+2)(a-2-1)=(a+2)(a-3)3.a^8-b^8=(a^4)^2-(b^4)^2=(a^4+b^4)(a^4-b^4)4
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以下五道因式分解哪些是错的?怎样改正?1.4(x-y)^2-9(x+y)^2=2^2(x-y)^2-3^2(x+y)^2=(2+3)(2-3)[(x-y)+(x+y)]*[(x-y)-(x+y)]=5*(-1)*2x*(-2y)=20xy2.a^2-4-a+2=(a+2)(a-2)-(a+2)=(a+2)(a-2-1)=(a+2)(a-3)3.a^8-b^8=(a^4)^2-(b^4)^2=(a^4+b^4)(a^4-b^4)4
以下五道因式分解哪些是错的?怎样改正?
1.4(x-y)^2-9(x+y)^2
=2^2(x-y)^2-3^2(x+y)^2
=(2+3)(2-3)[(x-y)+(x+y)]*[(x-y)-(x+y)]
=5*(-1)*2x*(-2y)
=20xy
2.a^2-4-a+2
=(a+2)(a-2)-(a+2)
=(a+2)(a-2-1)
=(a+2)(a-3)
3.a^8-b^8
=(a^4)^2-(b^4)^2
=(a^4+b^4)(a^4-b^4)
4.x^3+3x^2-2x-6
=x^2(x+3)-2(2x+3)
=(x+3)(x^2-2)
=(x+3)(x-2)(x+2)
5.15x^3n+9x^2n-6x^n
=3x^n(5x^2+3x-2)
=3x^n(5x+2)(x-1)
以下五道因式分解哪些是错的?怎样改正?1.4(x-y)^2-9(x+y)^2=2^2(x-y)^2-3^2(x+y)^2=(2+3)(2-3)[(x-y)+(x+y)]*[(x-y)-(x+y)]=5*(-1)*2x*(-2y)=20xy2.a^2-4-a+2=(a+2)(a-2)-(a+2)=(a+2)(a-2-1)=(a+2)(a-3)3.a^8-b^8=(a^4)^2-(b^4)^2=(a^4+b^4)(a^4-b^4)4
1,=(2x-2y)*(2x-2y)-(3x+3y)*(3x+3y)
=(2x-2y-3x-3y)*(2x-2y+3x+3y)
=-(5x+y)(x+5y)
2.a^2-4-a+2
=(a+2)(a-2)-(a-2)
=(a-2)(a+2-1)
=(a-2)(a+1)
3.a^8-b^8
=(a^4)^2-(b^4)^2
=(a^4+b^4)(a^4-b^4)
=(a^4+b^4)(a^2-b^2)(a^2+b^2)
=(a^4+b^4)(a-b)(a+b)(a^2+b^2)
4.x^3+3x^2-2x-6
=x^2(x+3)-2(x+3)
=(x+3)(x^2-2)
5.15x^3n+9x^2n-6x^n
=3x^n(5x^2n+3x^n-2)
=3x^n(5x^n-2)(x^n+1)