
The middle term should be factored in such a way that the sum of two numbers is -7x and their product is 10x2. These two factors are -5x and -2x. So re-writing the equation, we get:

Taking common, we get:

This means:
x - 5 = 0
⇒ x = 5
or
x - 2 = 0
⇒ x = 2
Therefore, the solution to the given equation are x = 2 and x = 5