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1. If a=5+15−1   and b = 5−15+1   then the value of (a2+ab+b2a2−ab+b2)    is = ?

Solution:
a+b=5+15−1+5−15+1=(5+1)2+(5−1)2(5−1)(5+1)=2[(5)2+1]5−1=2(5+1)4=3a.b=5+15−1×5−15+1=1Put value in expressiona2+ab+b2a2−ab+b2=(a+b)2−ab(a+b)2−3ab=32−132−3=9−19−3=43

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