MN ƠI GIÚP EM VỚI GẤP LẮM Ạ

EM SẮP ĐI HC RỒI Á(btvn nha)

4 câu 40đ nha, nhanh lên mn ơi

Đáp án:

`a)`

`(x+2)^2-(x-2)^2=16`

`=>(x+2-x+2)(x+2+x-2)=16`

`=>4.2x=16`

`=>8x=16`

`=>x=2`

Vậy `x=2`

`b)`

`(x+1)^3-3x^2=3x+x^3+2x^2-3`

`=>x^3+3x^2+3x+1-3x^2=x^3+2x^2+3x-3`

`=>x^3+3x+1=x^3+2x^2+3x-3`

`=>x^3-x^3-2x^2+3x-3x+1+3=0`

`=>-2x^2+4=0`

`=>-2x^2=-4`

`=>x^2=2`

`=>` \(\left[ \begin{array}{l}x=\sqrt{2}\\x=-\sqrt{2}\end{array} \right.\) 

Vậy `x\in{+-\sqrt{2}}`

`c)`

`(x-1)^3+3(x-3)^2-(x+2)(x^2-2x+4)=27`

`=>x^3-3x^2+3x-1+3(x^2-6x+9)-(x^3+2^3)=27`

`=>x^3-3x^2+3x-1+3x^2-18x+27-x^3-8=27`

`=>(x^3-x^3)+(3x^2-3x^2)+3x-18x+(-1+27-8)=27`

`=>-15x+18=27`

`=>-15x=9`

`=>x=-3/5`

Vậy `x=-3/5`

`d)`

`(3x+4)(3x-4)-(2x+5)^2=-1+5x^2`

`=>(3x)^2-4^2-(4x^2+20x+25)=5x^2-1`

`=>9x^2-16-4x^2-20x-25=5x^2-1`

`=>5x^2-20x-41=5x^2-1`

`=>5x^2-5x^2-20x=-1+41`

`=>-20x=40`

`=>x=-2`

Vậy `x=-2`