Jack was finding the special product of a perfect square binomial. Check Jack’s work and identify the mistake that he made, and find the correct product.
(4x−1) 2
= (4x) 2−2(4x) (1)+ (1) 2
=4x2−8x+1

Question

Jack was finding the special product of a perfect square binomial. Check Jack’s work and identify the mistake that he made, and find the correct product.
  (4x−1) 2 
= (4x) 2−2(4x) (1)+ (1) 2 
=4x2−8x+1

jadedry · Answer

As you mentioned a perfect square binomial, I assume you meant this: $$(4x -1) ^ 2$$

$$= (4x -1)(4x - 1)$$

You have to deal with this in bite-size pieces

First:

$$4x * (4x -1)$$ =

$$(4x * 4x) + (4x * (-1))$$ = $$16x^2 - 4x$$ 

Multiply the right side by the (-1) in the first equation

$$-1 * 4x + (-1) * (-1)$$

=$$-4x + 1$$

$$16x^2 - 4x + (-4x +1)$$ = $$16x^2 - 8x + 1$$ = Final product

He squared x in 4x^2 , but neglected to square the coefficient.