Đáp án: `a)(x+y+2)(x-y+2)` `b)2(x+y+2z)(x+y-z)` `c)(x-2)(5x-2)` `d)(x-2)(5x-2)` `e)(2x-1/2)(4x^2+x+1/4)` `f)(x+1)(1-5x)` Giải thích các bước giải: `a) x^2+4x+4-y^2=(x+2)^2-y^2=(x+y+2)(x-y+2)` `b) (x+y+2z)^2+(x+y-z)^2-9z^2` `=(x+y+2z)^2+(x+y-z-3z)(x+y-z+3z)` `=(x+y+2z)^2+(x+y-4z)(x+y+2z)` `=(x+y+2z)(x+y+2z+x+y-4z)` `=(x+y+2z)(2x+2y-2z)` `=2(x+y+2z)(x+y-z)` `c) (3x-2)^2-4x^2=(3x-2-2x)(3x-2+2x)=(x-2)(5x-2)` `d)` giống câu `c)` `e) 8x^3-1/8=(2x-1/2)(4x^2+x+1/4)` `f) (2x-1)^2-9x^2=(2x-1-3x)(2x-1+3x)=(-x-1)(5x-1)=(x+1)(1-5x)` Reply
Đáp án:
`a)(x+y+2)(x-y+2)`
`b)2(x+y+2z)(x+y-z)`
`c)(x-2)(5x-2)`
`d)(x-2)(5x-2)`
`e)(2x-1/2)(4x^2+x+1/4)`
`f)(x+1)(1-5x)`
Giải thích các bước giải:
`a) x^2+4x+4-y^2=(x+2)^2-y^2=(x+y+2)(x-y+2)`
`b) (x+y+2z)^2+(x+y-z)^2-9z^2`
`=(x+y+2z)^2+(x+y-z-3z)(x+y-z+3z)`
`=(x+y+2z)^2+(x+y-4z)(x+y+2z)`
`=(x+y+2z)(x+y+2z+x+y-4z)`
`=(x+y+2z)(2x+2y-2z)`
`=2(x+y+2z)(x+y-z)`
`c) (3x-2)^2-4x^2=(3x-2-2x)(3x-2+2x)=(x-2)(5x-2)`
`d)` giống câu `c)`
`e) 8x^3-1/8=(2x-1/2)(4x^2+x+1/4)`
`f) (2x-1)^2-9x^2=(2x-1-3x)(2x-1+3x)=(-x-1)(5x-1)=(x+1)(1-5x)`