Solve this set of equations...

This is for class IX X only

a(a+b+c) = 10
b(a+b+c) = 12
c(a+b+c) = 14

Find a, b, c

13 Answers

1
fibonacci ·

a/b = 5/6
b/c = 6/7
c/a = 7/5

so (a,b,c) = (5x , 6x , 7x)
5x(18x) = 10

so x= ±1/3

so (a,b,c) = (±5/3 , ± 2 , ±7/3 )

341
Hari Shankar ·

Also a+b+c = \frac{10}{a} = \frac{12}{b} = \frac{14}{c} = \frac{10+12+14}{a+b+c} = \frac{36}{a+b+c}

Hence a+b+c = ±6

62
Lokesh Verma ·

I guess this is the first time prophet sir missed a simpler solution?

or is it that you were showing an alternative solution?

just adding the three equations directly gives us

\left(a+b+c \right)^2=36

Hence a+b+c=±6

hence the solution :)

341
Hari Shankar ·

:D not the first time I have come up with a convoluted solution

62
Lokesh Verma ·

@fibonaci
(a,b,c) = (±5/3 , ± 2 , ±7/3 ) is not the right answer....

instead the righta answer shoudl be (a,b,c) = ±(5/3 ,2 ,7/3)

@Prophet sir: ;)

1
fibonacci ·

that is what i meant
either all positive at a time or all negative at a time

1
Rahul Singha ·

10/a=12/b=14/c
b=6a/5; c=7a/5
putting this in the first equ.
we get,a(a+6a/5+7a/5)=10
solving,we get a=5/3
similiarly we will get b and c

36
rahul ·

adding all the equations we get,

(a + b + c) = 6 or (a + b + c) = -6

Now, let us consider any of the three equations

firstly a(a + b + c) = 10
=> a + b + c = 10/a

=> b + c = (10 - a2)/a

=> 6 - a = (10 - a2)/a and -6 - a = (10 - a2)/a

=> 6a - a2 = 10 - a2 and -6a - a2 = 10 - a2
=> a = 5/3 or a = -5/3

and similiarly we get, a , b and c......

36
rahul ·

I must truly say i m a gadha....!!

Simple solution....

On adding all the three eqns. we get,

a + b + c = 6 or, a + b + c = -6

On putting these values of a + b + c in

all the three eqns. we get the values of a,b and c... simple...!!

1
kunl ·

hehe n i must truly agree u r one![3][3][3][3]...just kidding man...no issues!

36
rahul ·

@kunl -> How do u expect me to feel bad over something which is "a universal truth...lol".??

1
kunl ·

yeah right......we both belong to same school![1]

36
rahul ·

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