Solve 2x^2+7x> 15
2 x^2 + 7 x - 15 > 0
(2x - 3)(x + 5) > 0
if x = 3/2 the function is 0
if x = -5, the function is 0
the parabola opens up, the function is greater than zero to the left of -5 and to the right of +3/2
so
x > 3/2
x < -5
(2x - 3)(x + 5) > 0
if x = 3/2 the function is 0
if x = -5, the function is 0
the parabola opens up, the function is greater than zero to the left of -5 and to the right of +3/2
so
x > 3/2
x < -5