Let two positive intigers be such that their sum is 9 and the sum of their fourth powers is 2417. Find the two numbers?
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OpenStudy (anonymous):
@Arnab09 @yash2651995
Parth (parthkohli):
\( \color{Black}{\Rightarrow a + b = 9 }\)
\( \color{Black}{\Rightarrow a^4 + b^4 = 2417 }\)
Although you may attempt a trial and error here.
OpenStudy (lgbasallote):
this doesnt seem easy lol
Parth (parthkohli):
8,1 ; 7,2 ; 3,6 ; 4,5
Parth (parthkohli):
Check if any of em satisfy the second equation.
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OpenStudy (lgbasallote):
saw one :D
Parth (parthkohli):
Yes... I got it ;D
Parth (parthkohli):
Go put these in your calculator.
\( \color{Black}{\Rightarrow 8^4 + 1^4 }\)
\( \color{Black}{\Rightarrow 7^4 + 2^4 }\)
\( \color{Black}{\Rightarrow 6^4 + 3^4 }\)
\( \color{Black}{\Rightarrow 5^4 + 4^4 }\)
OpenStudy (yash2651995):
\[(a+b)^{4}= a ^{4}+b ^{4}+4(ab)(a+b)+6(ab)^{2}\]
find (ab) from here ..
then put it in \[(a-b)^{2}=(a+b)^{2}-4(ab)\]
then find a-b
use a+b=9 and a-b= ..what ever you get.. to find a and b
OpenStudy (yash2651995):
ab will be positive..^
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OpenStudy (shubhamsrg):
your formulla is wrong @yash2651995 please recheck
OpenStudy (yash2651995):
ya.. let me correct it..
OpenStudy (shubhamsrg):
formulla is (a+b)^4 = a^4 + 4a^3 b + 6a^2 b^2 + 4ab^3 + b^4
=> a^4 + b^4 + ab ( 4a^2 + 4b^2 + 6ab)
OpenStudy (shubhamsrg):
and a^2+ b^2 = 81 -2ab
now you can make this subsn and this should just do it