SOLUTION: hello sir/madam i am shreya from new delhi i want to ask if a,b,c are all non zero and a+b+c=0 prove that a^square/bc+b^square/ca+c^square/ab=3

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: hello sir/madam i am shreya from new delhi i want to ask if a,b,c are all non zero and a+b+c=0 prove that a^square/bc+b^square/ca+c^square/ab=3      Log On


   



Question 622302: hello sir/madam i am shreya from new delhi i want to ask if a,b,c are all non zero and a+b+c=0 prove that a^square/bc+b^square/ca+c^square/ab=3
Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
There may be a simpler way for this but here goes...

If
a%2Bb%2Bc+=+0
then
%28a%2Bb%2Bc%29%5E3+=+0
To cube the left side I am going to use the %28x%2By%29%5E3+=+x%5E3%2B3x%5E2y%2B3xy%5E2%2By%5E3 pattern with the "x" being "(a+b)" and the "y" being "c":
%28a%2Bb%29%5E3+%2B+3%28a%2Bb%29%5E2%2Ac+%2B+3%28a%2Bb%29%2Ac%5E2+%2Bc%5E3+=+0
For the %28a%2Bb%29%5E3 I will use this pattern again:

For the %28a%2Bb%29%5E2 I will use the %28x%2By%29%5E2+=+x%5E2%2B2xy%2By%5E2 pattern:

Multiplying we get:


Next I'll isolate the cubed terms on the left side by subtracting all the non-cubed terms from both sides:
a%5E3+%2Bb%5E3+%2Bc%5E3+=+-3a%5E2b+-3ab%5E2+-+3a%5E2%2Ac-6abc-3b%5E2%2Ac+-+3ac%5E2-3bc%5E2
Factoring out -3 on the right side:

Dividing both sides by abc. (We're told that a b and c are all non-zero so it is OK to divide by this.)

Splitting up the fractions:

Simplifying the fractions:

(Note that the left side is the expression we hope is equal to 3.) Adding the like fractions on the right side:

From a + b + c = 0:
  • Subtracting c from each side we get: a + b = -c
  • Subtracting b from each side we get: a + c = -b
  • Subtracting a from each side we get: b + c = -a
Substituting these expressions in for the numerators on the right side we get:

Simplifying the fractions further:
a%5E2%2Fbc+%2Bb%5E2%2Fac+%2Bc%5E2%2Fab+=+-3%28-1+%2B+%28-1%29%2B+2%2B+%28-1%29%29
Simplifying:
a%5E2%2Fbc+%2Bb%5E2%2Fac+%2Bc%5E2%2Fab+=+-3%28-1%29
a%5E2%2Fbc+%2Bb%5E2%2Fac+%2Bc%5E2%2Fab+=+3