Question

Thực hiện phép tính:
a)2x²y.(3x²-5xy+4y²)
b)(x²-9)²-(x+3).(x-3).(x²+9)
 

Answer 1

a:\(2x^2y\left(3x^2-5xy+4y^2\right)-6x^4y-10x^3y^2+8x^2y^3\)

b: \(\left(x^2-9\right)^2-\left(x+3\right)\left(x-3\right)\left(x^2+9\right)\)

\(=x^4-18x^2+81-\left(x^4-81\right)\)

\(=-18x^2+162\)

Answer 2

\(a,\) \(2x^2y\left(3x^2-5xy+4y^2\right)\)

\(=6x^4y-10x^3y^2+8x^2y^3\)

\(b,\) \(\left(x^2-9\right)^2-\left(x+3\right)\left(x-3\right).\left(x^2+9\right)\)

\(=\left(x^2-9\right)^2-\left(x^2-3^2\right)\left(x^2+9\right)\\ =\left(x^2-9\right)^2-\left(x^4-9^2\right)\\ =x^4-18x+81-x^4+81\\ =-18x+162\)