How do you solve the following system: -6x + y = -8, 2x+3y =4 6x+y=8,2x+3y=4?

1 Answer
Mar 17, 2018

See a solution process below:

Explanation:

Step 1) Solve the first equation for yy:

-6x + y = -86x+y=8

-6x + color(red)(6x) + y = -8 + color(red)(6x)6x+6x+y=8+6x

0 + y = -8 + 6x0+y=8+6x

y = -8 + 6xy=8+6x

Step 2) Substitute (-8 + 6x)(8+6x) for yy in the second equation and solve for xx

2x + 3y = 42x+3y=4 becomes:

2x + 3(-8 + 6x) = 42x+3(8+6x)=4

2x + (3 xx -8) + (3 xx 6x) = 42x+(3×8)+(3×6x)=4

2x - 24 + 18x = 42x24+18x=4

2x + 18x - 24 = 42x+18x24=4

(2 + 18)x - 24 = 4(2+18)x24=4

20x - 24 = 420x24=4

20x - 24 + color(red)(24) = 4 + color(red)(24)20x24+24=4+24

20x - 0 = 2820x0=28

20x = 2820x=28

(20x)/color(red)(20) = 28/color(red)(20)20x20=2820

(color(red)(cancel(color(black)(20)))x)/cancel(color(red)(20)) = 7/5

x = 7/5

Step 3) Substitute 7/5 for x in the solution to the first equation at the end of Step 1 and calculate y:

y = -8 + 6x becomes:

y = -8 + (6 xx 7/5)

y = (5/5 xx -8) + 42/5

y = -40/5 + 42/5

y = 2/5

The Solution Is:

x = 7/5 and y = 2/5

Or

(7/5, 2/5)