Question

Emily is solving the following System of equations using Substitution:

y=3x-4

y=2x+1

Her steps are shown below.

Part A

Click on the first step in which Emily made an error.​

3x-4=2x+1

5x-4=1

5x=5

x=1

y=3(1)-4=3-4=-1

(1,-1)


Part B

Explain what Emily did wrong and then what she should have done to make sure it was the correct answer.

Answer 1

Emily is solving the following system of equations using substitution:

y = 3x - 4

y = 2x + 1

Part A:

After substituting y's values:

3x - 4 = 2x + 1

What she did:

3x - 4 = 2x + 1

3x + 2x - 4 = 1

5x - 4 = 1

What she should have done:

3x - 4 = 2x + 1

3x - 2x - 4 = 1

x - 4 = 1

Part B:

This rule has not been followed: Sign changes when numbers shift from left to right of ' = 'sign.

Emily did not changed the sign of the number, 2x from + 2x to - 2x when it was moved from the right side to the left.