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Grade 9IIT JEE Entrance Exam

a , b , c , d are natural number such that a = bc , b = cd , c = da , d = ab. Then (a+b) (b+c) (c+d) (d+a) is equal to :
1. (a+b+c+d)^2
2.(a+d)^2 + (c+d)^2
3.(a+d)^2 +(b+c)^2
4.(a+c)^2 +(b+d)^2

Shivansh Singh

9 Years agoGrade 9

1 Answer

dip

9 Years ago

a=bc

b=cd

c=da

d=ab

therefore multiplying lhs & rhs separately abcd=(abcd)^2

or abcd=1 as abcd not equal to 0

since a,b,c,d are natural nos and abcd=1

therefore a=1,b=1,c=1,d=1

therefore dy putting valus of a,b,c,d in expression and options we see that

option 1 is correct

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