Tim x d) 125x^3 - 150x^2 = 9-60x e) 4(x-1)^2 - 25(2-3x)^2 =0 f) (2x+5)^2 + 4.(2x+5) = -4

Đáp án+Giải thích các bước giải:

 `d)`

`125x^{3}-150x^{2}=9-60x`

`<=>125x^{3}-150x^{2}+60x-9=0`

`<=>(5x)^{3}-3.(5x)^{2}.2+3.5x.2^{2}-2^{3}-1=0`

`<=>(5x-2)^{3}=1`

`<=>(5x-2)^{3}=1^{3}`

`<=>5x-2=1`

`<=>5x=3`

`<=>x=3/5`

Vậy `x=3/5`

`e)`

`4.(x-1)^{2}-25.(2-3x)^{2}=0`

`<=>[2.(x-1)]^{2}-[5.(2-3x)]^{2}=0`

`<=>(2x-2)^{2}-(10-15x)^{2}=0`

`<=>(2x-2-10+15x).(2x-2+10-15x)=0`

`<=>(17x-12).(-13x+8)=0`

`<=>17x-12=0` hoặc `-13x+8=0`

`<=>17x=12` hoặc `-13x=-8`

`<=>x=12/17` hoặc `x=8/13`

Vậy `x\in{12/17;8/13}`

`f)`

`(2x+5)^{2}+4.(2x+5)=-4`

`<=>(2x+5)^{2}+4.(2x+5)+4=0`

`<=>(2x+5)^{2}+2.(2x+5).2+2^{2}=0`

`<=>(2x+5+2)^{2}=0`

`<=>(2x+7)^{2}=0`

`<=>2x+7=0`

`<=>2x=-7`

`<=>x=-7/2`

vậy `x=-7/2`