Question 60448


Solution:

Here the equations are,
9x+y=10 and
x+4y=5

method of substitution:

consider the first equation,(also you can consider the second equation)

let us tAke the first one

9x+y=10

subtract  9x  from both sides.

==> 9x + y - 9x = 10 - 9x

==>  y = 10 - 9x

here we got the value of 'y' in terms of x. 

right?

now substitute this value of y in the second equation.

that is     x + 4 * ( 10 - 9x ) = 5

            x + 4 * 10 - 4 * 9x = 5
 
                   x + 40 - 36X = 5


Subtract 40 from both sides of the equation

==> x + 40 - 36x - 40 = 5 - 40

==> x - 36x = -35

==>    -35x = -35

now divide both sides of the equation by -35

==>  x = 1

understood?

now  substitute this value of  'x' , in the expression, y = 10 - 9x

==> y = 10 - 9 * 1

==> y = 10 - 9 

      =1

so the solution for the equations in

x=1
y=1