Question 820778
<pre>7x² + 15x - 18 = 0

You have to factor that.

There is only one way to break up 7x² and that is 7x and x:

(7x  )(x  ) = 0

But there are several ways to break up -18 = -18·1 = -9·2 = -6·3

A little trial and error by FOILing back to see if you get the
preceding trinomial, gives:

(7x-6)(x+3) = 0

Set each factor = 0

7x-6 = 0;  x+3 = 0
  7x = 6;    x = -3
   x = {{{6/7}}}

Two solutions:  {{{6/7}}} and -3

Edwin</pre>