Question

tìm x biết 

x ( 4x + 2 ) - ( 2x - 5 ) ( 2x + 5 ) = 1

Answer 1

Ta có \(x\left(4x+2\right)-\left(2x-5\right)\left(2x+5\right)=1\)

\(\Leftrightarrow4x^2+2x-\left(4x^2-25\right)=1\)

\(\Leftrightarrow4x^2+2x-4x^2+25=1\)

\(\Leftrightarrow2x=-24\)

\(\Leftrightarrow x=-12\)

Vậy x=-12

Answer 2

\(x\left(4x+2\right)-\left(2x-5\right)\left(2x+5\right)=1\)

\(4x^2+2x-\left(\left(2x\right)^2-5^2\right)=1\)

\(4x^2+2x-4x^2+25=1\)

\(2x+25=1\)

\(2x=-24\)

\(x=-12\)