Question

Làm các phép tính sau :

a,4(x-3y)(x+3y) + (2x-y) ^2

b, (2x-5)^2 +3(x-2)(x+2)

c,(x^2 + x - 3) (x^2-x +3)

Answer 1

\(a,4\left(x-3y\right)\left(x+3y\right)+\left(2x-y\right)^2\\ =4\left(x^2-9y^2\right)+4x^2-4xy+y^2\\ =4x^2-36y^2+4x^2-4xy+y^2\\ =8x^2-4xy-35y^2\)

\(b,\left(2x-5\right)^2+3\left(x-2\right)\left(x+2\right)=4x^2-20x+25+3x^2-12\\ =7x^2-20x+13\)

\(x,\left(x^2+x-3\right)\left(x^2-x+3\right)\\ =\left[x^2+\left(x-3\right)\right]\left[x^2-\left(x-3\right)\right]\\ =x^4-\left(x-3\right)^2\\ =x^4-x^2+6x-9\)