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SSC CGL 2018 PYQ — Question 89

SSC CGL Tier II Quant - 21/02/2018 • Quantitative Aptitude • Q89

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If a = (√3+√2)/(√3-√2) and b = (√3-√2)/(√3+√2) then

what is the value of a2+b2-ab ? 

Show answer & explanation

Correct answer: A

Explanation

The correct answer is option 1, i.e. 97

a = (√3+√2)/(√3-√2)

b = (√3-√2)/(√3+√2)

a =  (√3+√2) (√3+√2)/3-2

b =  (√3-√2) (√3-√2)/3-2

a = 5+2√6

b = 5-2√6

a2+b2 - ab = (5+2√6)2 + (5-2√6)2 - (5+2√6)(5-2√6)

= 25 + 24 + 20√6 + 25 +24 - 20√6 - 25 + 24 = 97