用乘法公式因式分解1.a²-25b²=2.-1/9+x²/4=3.(a+b)²-(a+c)²=4.16(x-y)²-49(x+y)²=5.m的四次方-n的四次方=6.(x-3)(x+12)-9x=

问题描述:

用乘法公式因式分解
1.a²-25b²=
2.-1/9+x²/4=
3.(a+b)²-(a+c)²=
4.16(x-y)²-49(x+y)²=
5.m的四次方-n的四次方=
6.(x-3)(x+12)-9x=

1.a²-25b²
=(a+5b)(a-5b)
2.-1/9+x²/4
=(x/2+1/3)(x/2-1/3)
3.(a+b)²-(a+c)²
=[(a+b)+(a+c)][(a+b)-(a+c)]
=(2a+b+c)(b-c)
4.16(x-y)²-49(x+y)²
=[4(x-y)+7(x+y)][(4(x-y)-7(x+y)]
=(4x-4y+7x+7y)(4x-4y-7x-7y)
=(11x+3y)(-3x-11y)
=-(11x+3y)(3x+11y)
5.m的四次方-n的四次方
=(m^2+n^2)(m^2-n^2)
=(m^2+n^2)(m+n)(m-n)
6.(x-3)(x+12)-9x
=x^2+9x-36-9x
=x^2-36
=(x+6)(x-6)