How do solve the following linear system?: -4x-2y=14 , -10x+7y=-2 ?

1 Answer
Jan 24, 2018

See a solution process below:

Explanation:

Step 1) Solve the first equation for y:

-4x - 2y = 14

color(red)(-1/2)(-4x - 2y) = color(red)(-1/2) xx 14

(color(red)(-1/2) xx -4x) + (color(red)(-1/2) xx -2y) = -7

2x + 1y = -7

2x + y = -7

2x - color(red)(2x) + y = -7 - color(red)(2x)

0 + y = -7 - 2x

y = -7 - 2x

Step 2) Substitute (-7 - 2x) for y in the second equation and solve for x:

-10x + 7y = -2 becomes:

-10x + 7(-7 - 2x) = -2

-10x + (7 xx -7) + (7 xx -2x) = -2

-10x + (-49) + (-14x) = -2

-10x - 49 - 14x = -2

-10x - 14x - 49 = -2

(-10 - 14)x - 49 = -2

-24x - 49 = -2

-24x - 49 + color(red)(49) = -2 + color(red)(49)

-24x - 0 = 47

-24x = 47

(-24x)/color(red)(-24) = 47/color(red)(-24)

(color(red)(cancel(color(black)(-24)))x)/cancel(color(red)(-24)) = -47/24

x = -47/24

Step 3) Substitute -47/24 for x in the solution to the first equation at the end of Step 1:

y = -7 - 2x becomes:

y = -7 - (2 xx -47/24)

y = -7 - (-47/12)

y = -7 + 47/12

y = (12/12 xx -7) + 47/12

y = -84/12 + 47/12

y = -37/12

The Solution Is:

x = -47/24 and y = -37/12

Or

(-47/24, -37/12)