Factoring y=5x^2-8x+4?

Question

How do you factor y=5x^2-8x+4? 

 

(x + 10)(x - 2)
(5x - 2)(x + 2)
(-5x + 2)(x + 2)
(x - 10)(x + 2)
(-5x - 2)(x - 2)

Answer 1

Reagan,

For a multiple choice question like this, you could simply foil each answer to see which one works. But I'll try to show you the factoring method I prefer.

 

y = 5x² - 8x + 4          multiply a*c = 20

 

So we need to find two numbers that multiply to 20 but add -8.

 

There are NONE!!!!!!      Normally I would just say OK use the quadratic formula. But that will not give you any of those answer choices. I suspect that either the 5 or the 4 should be negative.