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by resilient » Mon Mar 03, 2008 12:20 pm
(226)^2-(225)^2= ?

My approach: (225+1)^2=(225)^2= 225's cancel out and I am left with 1^2= 1

My answer is wrong

qa is 451. WHat did I do wrong?
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by smar83 » Mon Mar 03, 2008 12:47 pm
No, you do not do it that way.

The correct approach is to use the formula : (a^2-b^2) = (a+b)(a-b).

Just substitute your values and you would get:

a=226
b=225,

(226+225)(1)

your answer is 451.
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by smushkas » Mon Mar 03, 2008 12:48 pm
You should have done by ==> (a + b )^2 = a^2 + 2ab + b^2
( 226 )^2 - ( 225 )^2 = [ (225+1)^2 ] - (225)^2 = [ 225^2 + 225 + 225 + 1 ] - (225)^2 =
= 225^2 + 451 - 225^2 = 451

Hope it is clear!
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hmm

by resilient » Mon Mar 03, 2008 10:45 pm
so this question hinges on seeing the 225+1 but also to the see the common factor ?
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