What is the factored form of the expression?

4x2 – 81y2
A. (2x + 9)(2x – 9)
B. (2x + 9y)(2x – 9y)
C. (2x + 9y)2
D. (2x – 9y)2

Question

What is the factored form of the expression? 

4x2 – 81y2
  A. (2x + 9)(2x – 9) 	
  B. (2x + 9y)(2x – 9y) 	
  C. (2x + 9y)2 	
  D. (2x – 9y)2

anonymous · Answer

a multiple choice question ?

thesmartone · Answer

www.mathportal.org/calculators/polynomials-solvers/polynomial-factoring-calculator.php?formId=1&val4=4x^2-81y^2

thesmartone · Answer

Your question is in the format of (a^2-b^2)=(a+b)(a-b)

thesmartone · Answer

In this case a would be 2x and b would be 9y
So (2x+9y)(2x-9y)

anonymous · Answer

@Andresfon12  yes it is a mcq

anonymous · Answer

y= 0
X= 2

thesmartone · Answer

@alexxkayee She needed it factored not the roots...

thesmartone · Answer

And plus you cannot find roots because it has 2 variables..

anonymous · Answer

how would we do this then?

thesmartone · Answer

Using this formula
$$(a^2-b^2)=(a+b)(a-b) $$

thesmartone · Answer

In this case a would be 2x and b would be 9y
So $$(2x+9y)(2x-9y)=2x^2-9y^2 =4x^2-81y^2$$

thesmartone · Answer

So basically when it is factored it is (2x+9y)(2x-9y)

thesmartone · Answer

anonymous · Answer

i thought it was (C) but thank you for helping me understand that its (B)

anonymous · Answer

@TheSmartOne agree, also +-=- and -+=-