Question

tìm x biết (2x+5).(2x-7)-(2x-3)^2=36

Answer 1

`(2x+5)(2x-7)-(2x-3)^2=36`

`<=>4x^2-14x+10x-35-(4x^2-12x+9)=36`

`<=>4x^2-4x-35-4x^2+12x-9=36`

`<=>8x-44=36`

`<=>8x=80`

`<=>x=10`

Vậy `S={10}`

Answer 2

Ta có: \(\left(2x+5\right)\left(2x-7\right)-\left(2x-3\right)^2=36\)

\(\Leftrightarrow4x^2-14x+10x-35-\left(4x^2-12x+9\right)=36\)

\(\Leftrightarrow4x^2-4x-35-4x^2+12x-9=36\)

\(\Leftrightarrow8x-44=36\)

\(\Leftrightarrow8x=80\)

hay x=10

Vậy: S={10}