Question

Thực hiện phép tính:

a, 3xy(x-2y)-2x(x-xy)\(^2\)

b, 68\(^2\)+64.68+32\(^2\)

c, (x\(^3\)-6x\(^2\)+9x+14):(x-7)

d, (3x\(^2\)-\(\dfrac{1}{4}\)x)(5x\(^3\)-4x\(^2\)+6)

e, 2a\(^2\)b(x+y)-4ab\(^2\)(-x-y)

Answer 1

a) \(3xy\left(x-2y\right)-2x\left(x-xy\right)^2\)

\(=3x^2y-6xy^2-2x\left(x^2-2x^2y+\left(xy\right)^2\right)\)

\(=3x^2y-6xy^2-2x^3+2x^3y-2x^3y^2\)

b) \(68^2+64.68+32^2=\left(68+32\right)^2=100^2=10000\)

c) \(\left(x^3-6x^2+9x+14\right):\left(x-7\right)\)

\(=\left(x^2\left(x-7\right)-x\left(x-7\right)+2\left(x+7\right)\right):\left(x-7\right)\)

=?

Answer 2

a: \(=3x^2y-6xy^2-2x\left(x^2y^2-2x^2y+x^2\right)\)

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

b: \(=\left(68+32\right)^2=100^2=10000\)

c: \(=\dfrac{x^3-7x^2+x^2-7x+16x-112+126}{x-7}\)

\(=x^2+x+16+\dfrac{126}{x-7}\)

d: \(=15x^5-12x^4+18x^2-\dfrac{5}{4}x^4+x^3-1.5x\)

\(=15x^5-\dfrac{53}{4}x^4+x^3+18x^2-1.5x\)

e: \(=2a^2b^2+2a^2by+4axb^2+4ab^2y\)