Đáp án+Giải thích các bước giải:

`a)` `(x+2)^2 + (x+3)^2 - 2(x-2)(x-3) = 19`

`=>(x^2 + 4x + 4) + (x^2 + 6x + 9) - 2(x^2 - 3x - 2x + 6) = 19`

`=>x^2 + 4x + 4 + x^2 + 6x + 9 - 2(x^2 - 5x + 6) = 19`

`=>2x^2 + 10x + 13 - 2x^2 + 10x - 12 = 19`

`=>20x + 1 = 19`

`=>20x = 19 - 1`

`=>20x = 18`

`=>x = 18/20`

`=>x = 9/10`

`\text{Vậy}` `x = 9/10`

`b)` `(x+2)(x^2-2x+4) - x(x^2-5) = 15`

`=>(x^3 + 2^3) - (x^3 - 5x) = 15`

`=>x^3 + 8 - x^3 + 5x = 15`

`=>8 + 5x = 15`

`=>5x = 15 - 8`

`=>5x = 7`

`=>x = 7/5`

`\text{Vậy}` `x=7/5`

`c)` `(x-1)^3 + (2-x)(4+2x+x^2) + 3x(x+2) = 17`

`=>(x^3 - 3x^2 + 3x - 1) + (2^3 - x^3) + (3x^2 + 6x) = 17`

`=>x^3 - 3x^2 + 3x - 1 + 8 - x^3 + 3x^2 + 6x = 17`

`=>(x^3 - x^3) + (-3x^2 + 3x^2) + (3x + 6x) + (-1 + 8) = 17`

`=>9x + 7 = 17`

`=>9x = 17 - 7`

`=>9x = 10`

`=>x = 10/9`

`\text{Vậy}` `x = 10/9`

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