How do you solve the following system?: 8x - 2y = - 4 , 2x - 3y = 5 8x2y=4,2x3y=5

1 Answer
May 21, 2018

See a solution process below:

Explanation:

Step 1) Solve each equation for 8x8x:

  • Equation 1:

8x - 2y = -48x2y=4

8x - 2y + color(red)(2y) = -4 + color(red)(2y)8x2y+2y=4+2y

8x - 0 = -4 + 2y8x0=4+2y

8x = -4 + 2y8x=4+2y

  • Equation 2:

2x - 3y = 52x3y=5

color(red)(4)(2x - 3y) = color(red)(4) xx 54(2x3y)=4×5

(color(red)(4) xx 2x) - (color(red)(4) xx 3y) = 20(4×2x)(4×3y)=20

8x - 12y = 208x12y=20

8x - 12y + color(red)(12y) = 20 + color(red)(12y)8x12y+12y=20+12y

8x - 0 = 20 + 12y8x0=20+12y

8x = 20 + 12y8x=20+12y

Step 2) Because the left side of both equations are the same we can equate the right side of both equations and solve for yy:

-4 + 2y = 20 + 12y4+2y=20+12y

-4 - color(blue)(20) + 2y - color(red)(2y) = 20 - color(blue)(20) + 12y - color(red)(2y)420+2y2y=2020+12y2y

-24 + 0 = 0 + (12 - color(red)(2))y24+0=0+(122)y

-24= 10y24=10y

-24/color(red)(10)= (10y)/color(red)(10)2410=10y10

-12/5 = (color(red)(cancel(color(black)(10)))y)/cancel(color(red)(10))

-12/5 = y

y= -12/5

Step 3) Substitute -12/5 for y in either of the equations in Step 1 and calculate x:

8x = -4 + 2y becomes:

8x = -4 + (2 xx -12/5)

8x = -4 + (-24/5)

8x = -4 - 24/5

8x = (5/5 xx -4) - 24/5

8x = -20/5 - 24/5

8x = -44/5

8x xx 1/8 = -44/5 xx 1/8

8/8x = -44/40

x = -11/10

The Solution Is:

x = -11/10 and y= -12/5

Or

(-11/10, -12/5)