Knowing the roots first write the equation in factored form:
(X - 3/4)(x +5) = 0
Now use the FOIL method ( multiply each term in one set of parentheses by each term the other set:
X•x + x•5 -3/4•x -3/4•5
Simplify:
X^2 + 5x -3/4x -3 3/4
Combine like terms:
X^2+ 4 1/4x - 3 3/4
