is it necessary to densest?

Given that 98 = a + b + c \sqrt{98} = \sqrt{a}+\sqrt{b}+\sqrt{c} find the sum of all a , b , c a,b,c such that a > b > c > 0 a> b> c >0 and abc are integers


The answer is 42.

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2 solutions

Aareyan Manzoor
Dec 15, 2014

98 = 7 2 \sqrt{98}= 7\sqrt{2} there is 'only' one way to add 7 such that a > b > c > 0 a>b>c>0 4 + 2 + 1 = 7 4+2+1=7 so 7 2 = 4 2 + 2 2 + 2 7\sqrt{2}=4\sqrt{2}+2\sqrt{2}+\sqrt{2} 98 = 32 + 8 + 2 \sqrt{98}=\sqrt{32}+\sqrt{8}+\sqrt{2} a + b + c = 32 + 8 + 2 = 42 a+b+c = 32+8+2 = \boxed{42}

main thing is to show that there will not be more solutions

Kartik Sharma - 6 years, 5 months ago

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there are many solns...

Bharadwaj Rcr - 6 years, 5 months ago

answer can be 34... with a,b, c being 8,8,18.. try

Bharadwaj Rcr - 6 years, 5 months ago

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8=8 not a>b>c

Aareyan Manzoor - 6 years, 5 months ago
Anujit Roy
Dec 23, 2014

sqrt(98) = sqrt(a) + sqrt(b) + sqrt(c), a>b>c>0 and abc are integers. Find sum of a, b and c.

Solution : sqrt(98) = 7sqrt(2) = 4sqrt(2) + 2sqrt(2) + 1sqrt(2) =sqrt(2 * 4 4) + sqrt(2 * 2 2) + sqrt(2 * 1*1) = sqrt(32) + sqrt(8) + sqrt(2)

Let a = 32, b = 8, c = 2 So a>b>c>0 and abc = 32 * 8 * 2 = 512, which is an integer.

a + b + c = 32 + 8 + 2 = 42 Hence, the required sum is 42.

y cant it be 34.. with 2 sqrt(2)+ 2 sqrt(2) + 3 sqrt(2)... ?

Bharadwaj Rcr - 6 years, 5 months ago

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it is told that the numbers are in a ascending order, 2 of them cant be equal

Aareyan Manzoor - 6 years, 5 months ago

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