Ok so x=8, 18 are the zeroes or solutions for the given equation you will put this into a for called x-intercept form
(x-a)(x-b)=c
let c be 0 so when you find the Xs you can get the solutions (ex. x-8=0 => x=8)
[tex](x-8)(x-18)=0[/tex]
I am not sure what answer you wanted but here is how to get to the original equation
1) multiply the binomials => [tex]x(x-18)-8(x-18)[/tex]
2) you will get [tex]x^2-26x+144[/tex]
