# If #b# is the largest zero of #x^3-5x^2-x+5# then which of the following quadratic equations is it also a zero of?

##
**1)** #x^2-3x-10 = 0#

**2)** #x^2+3x-10 = 0#

**3)** #x^2-3x+10 = 0#

**4)** #x^2+3x+10 = 0#

**1)**

**2)**

**3)**

**4)**

##### 1 Answer

May 4, 2016

**1)**

#### Explanation:

First factor

#x^3-5x^2-x+5#

#=(x^3-5x^2)-(x-5)#

#=x^2(x-5)-1(x-5)#

#=(x^2-1)(x-5)#

#=(x-1)(x+1)(x-5)#

which has zeros:

So

Substituting this value of **1)** we find:

#x^2-3x-10 = 5^2-(3*5)-10 = 25-15-10 = 0#

So the answer is **1)**