How do solve the following linear system?: 3x - y = -6, 4x+3y=29 ?

1 Answer
Dec 11, 2017

color(red)[(x = 11/13) and (y = 111/13) OR

We can simplify the fractions and write the solutions as

color(red)[(x ~~ 0.8) and (y ~~ 8.5)

Explanation:

We are given the linear systems of equations given below:

3x -y = -6 color(blue)(Eqn.1)

4x +3y = 29 color(blue)(Eqn.2)

Multiply color(blue)(Eqn.1) by 3

Hence, color(blue)(Eqn.1) yields color(blue)(Eqn.3)

9x -3y = -18 color(blue)(Eqn.3)

4x +3y = 29 color(blue)(Eqn.2)

When we add color(blue)(Eqn.3) and color(blue)(Eqn.2) we get

9x -cancel(3y) = -18 color(blue)(Eqn.3)
4x +cancel(3y) = 29 color(blue)(Eqn.2)

rArr 13x = 11

Therefore, color(red)(x = 11/13)

Substitute this value of color(red)(x) in color(blue)(Eqn.1)

3x -y = -6 color(blue)(Eqn.1)

rArr 3(11/13) - y = -6

rArr (33/13) - y = -6

rArr - y = -6 - (33/13)

rArr - y = (-78 - 33)/13

rArr - y = -111/13

Divide both sides by -1 to get

rArr y =111/13

Hence, our final solutions are : -

color(red)[(x = 11/13) and (y = 111/13) OR

We can simplify the fractions and write the solutions as

color(red)[(x ~~ 0.8) and (y ~~ 8.5)