Find the x-intercepts.

Question

Find the x-intercepts of the graph of:

y= 2x² - 18x - 6.

Answer 1

x-intercept means, y = 0.

 

0 = 2x² - 18x - 6

 

Before applying factoring or quadratic formula, you can still simplify this because all the terms are divisible by 2.

 

0 = x² - 9x - 3 (The prime factors of -3 is just 3,-1 or -3,1, making it non-factorable since you need a sum of close to -9)

 

Therefore, use quadratic formula:

 

a = 1, b = -9, c = -3

 

x = [-(-9) ± √((-9)² - 4(1)(-3))]/2(1)

 

x = (9 ± √93)/2