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Solve this using the substitution method

-5x+4y=3
X=2y-15

User MitchellJ
by
4.5k points

1 Answer

3 votes

Answer:

x = 9 , y = 12

Explanation:

Solve the following system:

{4 y - 5 x = 3

x = 2 y - 15

Hint: | Perform a substitution.

Substitute x = 2 y - 15 into the first equation:

{4 y - 5 (2 y - 15) = 3

x = 2 y - 15

Hint: | Expand the left-hand side of the equation 4 y - 5 (2 y - 15) = 3.

4 y - 5 (2 y - 15) = 4 y + (75 - 10 y) = 75 - 6 y:

{75 - 6 y = 3

x = 2 y - 15

Hint: | Choose an equation and a variable to solve for.

In the first equation, look to solve for y:

{75 - 6 y = 3

x = 2 y - 15

Hint: | Isolate terms with y to the left-hand side.

Subtract 75 from both sides:

{-6 y = -72

x = 2 y - 15

Hint: | Solve for y.

Divide both sides by -6:

{y = 12

x = 2 y - 15

Hint: | Perform a back substitution.

Substitute y = 12 into the second equation:

{y = 12

x = 9

Hint: | Sort results.

Collect results in alphabetical order:

Answer: {x = 9 , y = 12

User Mutelogan
by
4.2k points