Question

write the following cubes in expanded form:(x-2/3y)^3​

Answer 1

we need to use (a-b)^3 formula here:

we know ; (a-b)^3 = a^3 - b^3 - 3ab(a-b)

in this case a= x

b= 2/3y

so by substituting terms we get,

x^3 - (2/3y)3 - 3x*2/3y( x-2/3y)

= x^3 - 8/27y3 - 2x/y(x-2/3y)

if you want to expand further, we get,

x^3 -8/27y^3 - 2x/y(x) - 2x/y(2/3y)

= x^3 - 8/27y^3 - 2x^2/y - 4x/3y2