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Use slopes and y-intercepts to determine if the lines 6x+y=−1 and −2x−5y=1 are parallel.

User Teekin
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1 Answer

16 votes
16 votes

Answer:

The two lines are not parallel.

Explanation:

Every linear equation follows this structure:

y = mx + b

y is the y value

x is the x value

m is the gradient/slope of the line

b (or sometimes c) is the y-intercept of the line

Firstly, we have to get the y term on one side by itself.

6x + y = -1

-6x -6x

y = -6x - 1

-2x -5y = 1

+2x +2x

-5y = 2x + 1

Secondly, we make it so the y term is just the y value.

The first equation is already like this, so we don't need to do anything to that.

-5y = 2x + 1

÷ -5 ÷ -5

y = (2x + 1) / -5

This can be expanded and simplified to:

y = -2/5x - 1/5

Thirdly, we have to compare the slopes and y-intercepts.

y = -6x - 1

y = 2/5x - 1/5

If the slopes are the same and the y-intercepts are different, they are parallel. However, the slopes are different, therefore they are not parallel.

User Gourneau
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