203,917 views
21 votes
21 votes
Substitution method algebra 1

y=-4x+5
y=3x-16

i know what to do just not sure how to get the final answer. aka im stuck on how to solve essentially

User Yasin Br
by
2.5k points

2 Answers

12 votes
12 votes

Answer:

x = 3; y = -7

Explanation:

Both equations are solved for y.

Let's substitute what y is equal to in the first equation, -4x + 5, for y in the second equation.

The original second equation is:

y = 3x - 16

Now we plug in -4x + 5 for y in the second equation.

-4x + 5 = 3x - 16

Subtract 3x from both sides.

-7x + 5 = -16

Subtract 5 from both sides.

-7x = -21

Divide both sides by -7.

-7x/-7 = -21/-7

x = 3

Now that we know the value of x, we use substitution again.

Take the first original equation, y = -4x + 5, and substitute 3 for x. Then solve for y.

Here is the first original equation:

y = -4x + 5

Substitute 3 for x:

y = -4(3) + 5

y = -12 + 5

y = -7

The solution is: x = 3; y = -7

We can check the solution to make sure it is correct.

Take each original equation and plug in the values we found for x and y. Simplify both sides and see if they are equal. If the two sides are equal, the solution is correct.

Check first equation:

y = -4x + 5

-7 = -4(3) + 5

-7 = -12 + 5

-7 = -7

The solution works on the first equation.

Check second equation:

y = 3x - 16

-7 = 3(3) - 16

-7 = 9 - 16

-7 = -7

The solution works in the second equation.

This shows that our solution is correct.

Answer: x = 3; y = -7

User Greg Finzer
by
3.2k points
22 votes
22 votes

Answer:

x = 3

y = -7

Explanation:

y = -4x + 5

y = 3x - 16

Substitute y in the first equation with 3x - 16

3x - 16 = -4x + 5

+4x +4x

7x - 16 = 5

+16 +16

7x = 21

÷7 ÷7

x = 3

Then, put x = 3 in y = -4x + 5

y = -4(3) + 5

y = -12 + 5

y = -7

User Adeyinka
by
2.8k points