Đáp án+Giải thích các bước giải:
`(5x+15)^3-(3x+5)^3=(2x+10)^3`
`<=>(5x+15-3x-5)(25x^2+150x+225+(5x+15)(3x+5)+9x^2+30x+25)=(2x+10)^3`
`<=>(2x+10)(34x^2+180x+250+15x^2+25x+45x+75)-(2x+10)^3=0`
`<=>(2x+10)(49x^2+250x+325)-(2x+10)(2x+10)^2=0`
`<=>(2x+10)(49x^2+250x+325-4x^2-40x-100)=0`
`<=>(2x+10)(45x^2+210x+225)=0`
`<=>2(x+5)(45x^2+135x+75x+225)=0`
`<=>(x+5)[45x(x+3)+75(x+3)]=0`
`<=>(x+5)(x+3)(45x+75)=0`
`<=>[(x=-5),(x=-3),(45x=-75):}`
`<=>[(x=-5),(x=-3),(x=-5/3):}`
Vậy `x\in{-5;-3;-5/3}`
