Question

 

Answer 1

a)(15x - 6y)\(\left(\dfrac{-2y}{3}\right)\)

= -10xy+ 4\(y^2\)

b)\(\left(\dfrac{3}{4}x^2y-\dfrac{3}{2}xy^2-\dfrac{5}{3}y^3\right)\dfrac{4}{3}xy\)

= \(x^3y^2-2x^2y^2-\dfrac{20}{9}xy^4\)

c) \(\dfrac{-7}{5}x\left(15-25x^2\right)\)

= -21x - 35\(x^3\)

d) (6x+1)(2x-3)+(3x+1)(2-2x)

= 12x\(^2\)-18x+2x-3+6x-6x\(^2\)+2-2x

 

Answer 2

P) \(\left(y^2+2\right)\left(y-4\right)-\left(2y^2+1\right)\left(\dfrac{1}{2}y-2\right)\)

\(=y^3-4y^2+2y-8-\left(y^3-4y^2+\dfrac{1}{2}y-2\right)\)

\(=y^3-4y^2+2y-8-y^3+4y^2-\dfrac{1}{2}y+2\)

\(=\dfrac{3}{2}y-6\)

p)(x-2)(x\(^{^2}\)-5x+1)-x(x\(^2\)+11)

\(=x^3-5x^2+x-2x^2+10x-2-x^3-11x\)

\(=-7x^2-2\)

Answer 3

g) 6(3a+4b)-8(5a-b)+(a-b)

= 18a + 24b - 40a + 8b +a -b

= -21a+31b

h) \(5x\left(4x^2-2x+1\right)-2x\left(10x^2-5x-2\right)\)

= 20x\(^3\)-10x\(^2\)+5x-20x\(^3\)+10x\(^2\)+4x

= 9x

i) 6xy(xy-y\(^2\))-8x\(^2\)(x-y\(^2\)) + 5y\(^2\)(x\(^2-xy\))

=\(6x^2y^2-6xy^3-8x^3+8x^2y^2+5x^2y^2-5xy^3\)

= \(19x^2y^2-11xy^3-8x^3\)

k) (3x-4)(5y-1)

= 15xy -3x-20y+4

m) \(\left(2x^2-3xy+5y^2\right)\left(x-y\right)\)

= \(2x^3-2x^2y-3x^2y+3xy^2+5xy^2-5y^3\)

=\(2x^3-5x^2y+8xy^2-5y^3\)

n) (2x-3y)\(\left(4x^2+6xy+9y^2\right)\)

= \(8x^3+12x^2y+18xy^2-12x^2y-18xy^2-27y^3\)

= \(8x^3-27y^3\)

 

Answer 4

Bổ sung câu e)

e) \(\dfrac{-1}{3}xy\left(-9xy+15yz\right)+3x^2\left(2yz^2-yz\right)\)

\(3x^2y^2-5xy^2z+6x^2yz^2-3x^2yz\)