(root(9 + root(80)) + root(9 - root(80)))^2.
OA is 20
My question is when I see a question like this I am not sure if I should try to FOIL it or try to Add or Subtract it. Can some share what is the fastest way to attack a question like this.
Vineet
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vineetbatra
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sanjana
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Whenever you see anything of the form (a+b)^2 or a^2-b^2 just try and factorise using the formula. This will almost always eliminate the root in the question.
For this question you just need to apply (a+b)^2
you get,
9+√80 + 9-√80 + 2√(9+√80)(9-√80)
=18+2√(81-80) --> applying a^2-b^2 = (a+b)(a-b)
=18+2 = 20
For this question you just need to apply (a+b)^2
you get,
9+√80 + 9-√80 + 2√(9+√80)(9-√80)
=18+2√(81-80) --> applying a^2-b^2 = (a+b)(a-b)
=18+2 = 20
