Question

How do you solve `(20-r)^(1/2)=r`?

Answer 1

`r= 4 or -5`

Explanation:

`(20-r)^(1/2) = r`

`sqrt(20-r) = r`

Square both sides:
`20-r=r^2`

`r^2+r-20=0`

Factorise:
`(r-4)(r+5)=0`

`r = 4 or -5`