Question

I need help to figure out how to solve this problem.

Determine whether each pair of equations represents parallel lines.
y=5-3x
3x-y=8

Answer 1

what do you get when you solve

3x-y=8

for y

Answer 2

You know that lines are parallel if they have equal slopes so put both equations in y=mx+b form in order to compare their slopes (m).

Answer 3

would it be y=3?

Answer 4

What do you mean by y=3?

Answer 5

I used the formula y=mx+b like Twis7ed said. I may have done it wrong but that is the answer i came up with.

Answer 6

solve 3x-y=8 for y to get

3x-y=8

3x-y-3x=8-3x

-y = 8 - 3x

-y = -3x + 8

y = 3x - 8

Answer 7

Now compare slopes

Answer 8

Keep in mind that

y=5-3x

is the same as

y=-3x+5

Answer 9

I am even more confused now. Is the 3x the point on the graph on the x axis and the 5 the point on the y axis?

Answer 10

y=5-3x

turned into

y=-3x+5

The slope of this is -3 (since that's the number in front of the x)

-------------------------------------------------------

3x-y=8

turned into

y = 3x - 8

which has a slope of 3

Answer 11

So what can you tell me about these two lines if you know the slopes are -3 and 3

Answer 12

The lines are not parallel

Answer 13

good, the two slopes would have to be equal if the lines were parallel

Answer 14

Thank you. That was more helpful that the book.