# How do you solve #x^2 + 2x - 15 = 0 #?

##### 2 Answers

Apr 12, 2018

#### Explanation:

#"the factors of - 15 which sum to + 2 are + 5 and - 3"#

#rArr(x+5)(x-3)=0#

#"equate each factor to zero and solve for x"#

#x+5=0rArrx=-5#

#x-3=0rArrx=3#

Apr 12, 2018

#### Explanation:

**Rules for factorising:**

#ax^2+bx+c=0# #m xx n = c# #m + n = b# #:.(x+m)(x+n) = 0#

**In this case:**

**Either of the brackets must be equal to 0.**

Assuming (x+5) = 0:

Assuming (x-3) = 0: