Question

rút gọn biểu thức : A=(3x³+3x+1).(3x³-3x+1)-(3x³+1)² 

Answer 1

\(A=\left(3x^3+3x+1\right)\left(3x^3-3x+1\right)-\left(3x^3+1\right)^2\)

    \(=\left[\left(3x^3+1\right)+3x\right]\left[\left(3x^3+1\right)-3x\right]-\left(3x^3+1\right)^2\)

    \(=\left(3x^3+1\right)^2-\left(3x\right)^2-\left(3x^3+1\right)^2\)

    \(=-\left(3x\right)^2\)

     \(=-9x^2\)

Answer 2

\(\left(3x^3+3x+1\right)\left(3x^3-3x+1\right)-\left(3x^3+1\right)^2=\left(3x^3+1\right)^2-\left(3x\right)^2-\left(3x^3+1\right)^2=-9x^2\)