`x × (3x + 2)+(x+1)^2-(2x-5)(2x+5)=-12`
`⇔ 3x^2+2x+(x+1)^2−(2x−5)(2x+5)=−12`
`⇔ 3x^2+2x+x^2+2x+1−(2x−5)(2x+5)=−12`
`⇔ 4x^2+2x+2x+1−(2x−5)(2x+5)=−12`
`⇔ 4x^2+4x+1−(2x−5)(2x+5)=−12`
`⇔ 4x^2+4x+1−((2x)^2−25)=−12`
`⇔ 4x^2+4x+1−(2^2x^2−25)=−12`
`⇔ 4x^2+4x+1−(4x^2−25)=−12`
`⇔ 4x^2+4x+1−4x^2+25=−12`
`⇔ 4x+1+25=−12`
`⇔ 4x+26=−12`
`⇔ 4x=−12−26`
`⇔ 4x=−38`
`x = (-38)/4`
`x = -19/2`
Cho mình xin hay nhất nha bạn!!!!
@Drew Mclntyre
