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

1 Answer
Don't Memorise
Nov 14, 2015

#color(blue)((a+11b)(a-11b)#

Explanation:

#a^2−121b^2#
This expression can be rewritten as #(a)^2−(11b)^2#

Now, as per the below property,
#color(blue)(x^2-y^2=(x+y)(x-y)#, we can rewrite the expression as:

#(a)^2−(11b)^2=color(blue)((a+11b)(a-11b)#
(Here, #x=a,y=11b# )

So the factorised form of the expression is:
#=color(blue)((a+11b)(a-11b)#

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