algebra I
posted by Julia .
how do I solve for 16x^2+56x120

In google type:
quadratic equation online
When you see list of results click on:
Free Online Quadratic Equation Solver:Solve by Quadratic Formula
When page be open in rectangle type:
16x^2+56x120=0
and click option: solve it
You will see solution stepby step 
I assume you meant
solve 16x^2+56x120=0 , you must have an "equation" to solve for it.
divide by 8
2x^2 + 7x  15 = 0
(2x3)(x+5) = 0
x = 3/2 or x = 5