How do you solve 4x + 3y = - 4 and 3x - 7y = 34?

1 Answer
Jan 29, 2017

See the entire solution process below:

Explanation:

Step 1) Solve the first equation for xx:

4x + 3y = -44x+3y=4

4x + 3y - color(red)(3y) = -4 - color(red)(3y)4x+3y3y=43y

4x + 0 = -4 - 3y4x+0=43y

4x = -4 - 3y4x=43y

(4x)/color(red)(4) = (-4 - 3y)/color(red)(4)4x4=43y4

(color(red)(cancel(color(black)(4)))x)/cancel(color(red)(4)) = -4/4 - (3y)/4

x = -1 - 3/4y

Step 2) Substitute -1 - 3/4y for x in the second equation and solve for y:

3(-1 - 3/4y) - 7y = 34

-3 - 9/4y - 7y = 34

color(red)(3) - 3 - 9/4y - 7y = color(red)(3) + 34

-9/4y - 7y = 37

-9/4y - (4/4 xx 7)y = 37

-9/4y - 28/4y = 37

-37/4y = 37

-color(blue)(4)/color(red)(37) xx -37/4y = -color(blue)(4)/color(red)(37) xx 37

cancel(-color(blue)(4))/cancel(color(red)(37)) xx color(red)(cancel(color(black)(-37)))/color(blue)(cancel(color(black)(4)))y = -color(blue)(4)/cancel(color(red)(37)) xx color(red)(cancel(color(black)(37)))

y = -4

Step 3) Substitute -4 for y in the solution to the first equation at the end of Step 1 and calculate x:

x = -1 - (3/4 xx -4)

x = -1 - (3/color(red)(cancel(color(black)(4))) xx -color(red)(cancel(color(black)(4))))

x = -1 - (-3)

x = -1 + 3

x = 2

The solution to this problem is:

x = 2 and y = -4