Question

45^2+40^2-15^2+80x45

Answer 1

\(45^2+40^2-15^2+80.45\)

\(=45^2+2.40.45+40^2-15^2\)

\(=\left(45+40\right)^2-15^2=85^2-15^2\)

\(=\left(85-15\right)\left(85+15\right)=7000\)

Answer 2

\(45^2+40^2-15^2+80x45\\ =\left(45+40\right)^2-15x^2\\ =\left(45+40-15\right)\left(45+40+15\right)\\ =70.100=70000\)

Answer 3

tính nhanh