Let $7x^2 + 5x = h$. What value of $h$ will give us exactly one solution for $x$?
7x^2 + 5x - h = 0 for only ONE solution, the discriminant must = 0
b^2 - 4ac = 0
5^2 - 4(7)(-h)
25 + 28 h = 0
h = -25/28