Question

I am supposed to write a quadratic equation using only the solutions and I am only given one solution:4.

It can't be (x-4)=0. Can I use 0 to make (x-4)(x+0)=0?

Answer 1

I would make 4 a double root, so then
(x-4)(x-4)=0
x^2 - 8x + 16 = 0

Answer 2

it is long and yellow