Question

 Tìm x biết:
              [2x+1].[2x-3]-[4x+1].[x+2]=8

Answer 1

\(\left(2x+1\right).\left(2x-3\right)-\left(4x+1\right)\left(x+2\right)=8\\ 4x^2-6x+2x-3-4x^2-8x-x-2=8\\ -13x-5=8\\ -13x=13\\ x=-1\)

Answer 2

Ta có: \(\left(2x+1\right)\left(2x-3\right)-\left(4x+1\right)\left(x+2\right)=8\)

\(\Rightarrow\left[2x\left(2x-3\right)+2x-3\right]-\left[4x\left(x+2\right)+x+2\right]=8\)

\(\Rightarrow\left(4x^2-6x+2x-3\right)-\left(4x^2+8x+x+2\right)=8\)

\(\Rightarrow4x^2-4x-3-4x^2-8x-x-2=8\)

\(\Rightarrow-13x-5=8\)

 

\(\Rightarrow x=-1\)