How do you solve x squared plus 2x minus 15 equals 0?

Answer 1

There are many ways to solve it, such as completing the square or using the quadratic formula, but I'll assume you mean by factoring it.

In a problem like this, you start off by figuring out the factors of 15. In this case, they are 1, 3, 5, and 15. That means that the polynomial factors out to be either (x+-3)(x+-5) or (x+-1)(x+-15) where +- means either plus or minus. Also, one of the factors must have a plus and the other a minus because 15 is negative in the polynomial. By a simple observation, or by guess and checking, we find it to factor into (x+5)(x-3) = 0, or x = -5, 3