Question

How do you factor `y^3-18y^2+81y`?

Answer 1

`y^3-18y^2+81y`
`color(white)("XXXX")` `= y(y-9)^2`

Explanation:

`y^3-18y^2+81y`
If we extract the obvious common factor from each term
`color(white)("XXXX")` `=y(y^2-18y+81)`
With a bit of thought the second factor can be seen as a square
`color(white)("XXXX")` `=y(y-9)(y-9)`