Three equations, three unknowns:?

Question

Three equations, three unknowns:

a - b + c = -10
4a + 2b + c = -1
9a + 3b + c = -6

find, a,b,c

Answer 1

a-b+c- -10.....(eqn1)
4a+2b+c= -1.....(eqn. 2)
9a+3b+c= -6......(eqn 3)
Subtracting eqn.1 from eqn 2,we get
3a+3b=9.........(eqn. 4)
Subtracting eqn 2 from eqn. 3,we get
5a+b= -5........,(eqn 5)
Multiplying eqn. 4 by 1 and eqn 5 by 3 we get.
3a+3b=9
15a+3b= -15
(subtracting) -12a=24
=>a=24/-12= -2
Putting the value of a in eqn.5 ,we get
5*-2+b=-5
=> b= -5+10=5
Putting the values of a and b in eqn. 1 we get,
-2-5+c=-10
=>-7+c= -10
=>c=-10+7= -3
Therefore a= -2,b=5 and c= -3

Answer 2

thats very easy question, better check for example in your text book.