How do you factor completely #a^2 - 121b^2#?

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Answer 1 · 2018-06-13T06:07:21

#a^2-121b^2 = (a-11b)(a+11b)#

The difference of sqares identity can be written:

#A^2-B^2 = (A-B)(A+B)#

Given:

#a^2-121b^2#

Note that both #a^2# and #121b^2 = (11b)^2# are perfect sqares.

So we can use the difference of squares identity with #A=a# and #B=11b# to find:

#a^2-121b^2 = a^2-(11b)^2 = (a-11b)(a+11b)#

Answer 2 · 2018-06-13T06:08:36

Shown below...

Use difference of two squares:

#(A^2-B^2) = (A+B)(A-B) #

#=> ( (a)^2 - (11b)^2 ) #

#=> (a+11b)(a-11b) #