Question

Use substitution to solve the equation. Make sure your answer is simplified.

3x+2y=4
if y=4x+7
show steps.

Answer 1

Answer:

1. If you know y, change „y” into equation it is:

3x + 2y = 4, and change to:

3x + 2(4x+7) = 4

2. Shorten, by multiplicating numbers before brackets (2), by other nums in bracket (4x and y). Don’t forget to count symbol before number, and if it doesn’t have symbol before, it has plus.

3x + 8x + 14 = 4
11x + 14 = 4

3. Change side of unknown variables to right (its already here, so don’t change), and numbers to left, without forgetting to change sign (from + to -, and from - to +).:
11x + 14 = 4
11x = 4 - 14
11x = -10

4. Divide both sides by number of x (its 11) to get the answer:

11x = -10 |:11
x =
`-(10)/(11)`

So now if you have x, change “x” to score, and solve equation for y:


`image`

1. Change unknown variable to left (its already here), and numbers to right, without forgetting to change the sign:


`image`

2. Divide both sides by 2 (number of y), to get the answer:


`image`

3. Divide knowing when you divide 2 fraction, you multiply by reciprocal:


`image`

Proof it’s right:
3x + 2y = 4


`image`, so this is right.

Hope this helps!