Đáp án + Giải thích các bước giải:
`9)`
`(3x+2)/(x^2-12x+20)+(4x+3)/(x^2+6x-16)=(7x+11)/(x^2-2x-80)`
ĐKXĐ : `x ne -8;2;10`
`<=> (3x+2)/((x-10)(x-2)) + (4x+3)/((x+8)(x-2)) = (7x+11)/((x-10)(x+8))`
`<=> ((3x+2)(x+8)+(4x+3)(x-10))/((x-10)(x-2)(x+8))=((7x+11)(x-2))/((x-10)(x-2)(x+8))`
`=> (3x+2)(x+8)+(4x+3)(x-10)=(7x+11)(x-2)`
`<=> 3x^2+24x+2x+16+4x^2-40x+3x-30=7x^2-14x+11x-22`
`<=> (3x^2+4x^2-7x^2)+(24x+2x-40x+3x+14x-11x)=-22+30-16`
`<=> -8x=-8`
`<=> x=1 \ \ (tmđk)`
Vậy `x=1`
`10)`
`(2x-5)/(x^2+5x-36)-(x-6)/(x^2+3x-28)=(x+8)/(x^2+16x+63)`
ĐKXĐ : `x ne 4;-9;-7`
`<=> (2x-5)/((x-4)(x+9))-(x-6)/((x-4)(x+7))=(x+8)/((x+7)(x+9))`
`<=> ((2x-5)(x+7)-(x-6)(x+9))/((x-4)(x+7)(x+9))=((x+8)(x-4))/((x-4)(x+7)(x+9))`
`=> (2x-5)(x+7)-(x-6)(x+9)=(x+8)(x-4)`
`<=> 2x^2+14x-5x-35-(x^2+9x-6x-54)=x^2-4x+8x-32`
`<=> 2x^2+9x-35-x^2-3x+54=x^2+4x-32`
`<=> (2x^2-x^2-x^2)+(9x-3x-4x)=-32-54+35`
`<=> 2x=-51`
`<=> x=-51/2 \ \ (tmđk)`
Vậy `x=-51/2`
