Question

  giải giúp vs

Answer 1

a: \(A=\left(2x-1\right)\left(2x+1\right)-4x^2\)

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

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

b: \(105^2-5^2=\left(105-5\right)\left(105+5\right)=100\cdot110=11000\)

\(77^2-23^2=\left(77-23\right)\left(77+23\right)=54\cdot100=5400\)