Ominous powers

Algebra Level 1

If, a+b+c=0, 4a+2b+c=0, a+2b+4c=0, find a^2013+b^2013+c^2013. [^ denotes to the power of]


The answer is 0.

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4 solutions

Tom Capizzi
Sep 2, 2016

The determinant of the coefficient matrix of the LHS is non-zero (-6). The column vector of the RHS is all zeroes. To solve for a, b and c, we replace a column in the coefficient matrix with the column vector from the RHS. The determinant of a matrix with any column all zero is also zero. Therefore, a = b = c = 0/(-6) = 0. Zero to any non-zero power is also 0, so the answer is 0.

Caeo Tan
Nov 11, 2014

a+b+c=0, 4a+2b+c=0, a+2b+4c=0 (4a+2b+c)-(a+b+c)=3a+b=0 (a+2b+4c)-(a+b+c)=b+3c=0 (4a+2b+c)-(a+2b+4c)=3a-3c=0 a=c from 3a-3c=0 b=-3a from 3a+b=0 a+a-3a=0 -a=0, a=0 or c+c-3c=0, c=0 so a=0, b=0, c=0

Rakshit Pandey
Jul 30, 2014

a + b + c = 0 E q . 1 a+b+c=0\rightarrow Eq.1
4 a + 2 b + c = 0 E q . 2 4a+2b+c=0\rightarrow Eq.2
a + 2 b + 4 c = 0 E q . 3 a+2b+4c=0\rightarrow Eq.3
Subtracting E q . 3 Eq.3 and E q . 2 Eq.2 , we get,
3 a 3 c = 0 3a-3c=0
a = c E q . 4 \Rightarrow \boxed {a=c}\rightarrow Eq. 4
Now, using E q . 4 Eq.4 in E q . 2 Eq.2 , we get,
4 c + 2 b + c = 0 4c+2b+c=0
b = ( 5 c ) 2 \Rightarrow b=\frac{(-5c)}{2}
So, a : b : c = 1 : ( 5 ) 2 : 1 a:b:c=1:\frac{(-5)}{2}:1
So, a = x a=x , b = ( 5 x ) 2 b=\frac{(-5x)}{2} and c = x c=x .
Putting these values in E q . 1 Eq.1 ,
x + ( 5 x ) 2 + x = 0 x+\frac{(-5x)}{2}+x=0
2 x + ( 5 x ) 2 = 0 2x+ \frac{(-5x)}{2}=0
( x ) 2 = 0 \Rightarrow \frac{(-x)}{2}=0
x = 0 \Rightarrow x=0
So,
a = x = 0 \boxed {a=x=0} , b = ( 5 x ) 2 = 0 \boxed {b=\frac{(-5x)}{2}=0} & c = x = 0 \boxed {c=x=0} .
Hence, a 2013 + b 2013 + c 2013 = 0 \boxed {a^{2013}+b^{2013}+c^{2013}=0} .




Janercy Deng
Jul 23, 2014

solve for the variables, a = b = c = 0, so the answer is 0

from eq 2 and eq3 a=c b=-3c .. so a:b:c=1:-3:1 but hold on a+b+c=0 , so a=b=c=0 ..hence the answer

Devank Yadav - 6 years, 10 months ago

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How did you get b = ( 3 c ) b=(-3c) ?

Rakshit Pandey - 6 years, 10 months ago

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