x(x + 7.5) > 38
x² + 7.5x - 38 > 0
First, find the solutions of x² + 7.5x - 38 = 0
I used the quadratic formula and got x = 3.465 and x = -10.965
These two numbers divide the x-axis into three groups.
So, there are three groups (x < -10.965) (-10.965 < x < 3.465) (x > 3.465)
Try any number from the first group; I'll choose -20; and put it back into the original inequality:
x(x + 7.5) > 38 ===> -20(-20 + 7.5) = 250 and that's > 38 go this section works.
Try any number from the second group; I'll choose 0; and put it back into the original inequality:
x(x + 7.5) > 38 ===> 0(0 + 7.5) = 0 and that's not > 38 go this section doesn't works.
Try any number from the third group; I'll choose 10; and put it back into the original inequality:
x(x + 7.5) > 38 ===> 10(10 + 7.5) = 175 and that's > 38 go this section works.
Since the first group and the third group both work, the answer is: x < -10.965 or x > 3.465.