I have a few more questions.No problem, happy to help!

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  • Thread starter mathdad
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In summary, when solving for the equation of a line, the y-intercept is found by substituting the point on the line into the point-slope formula. The slope is found by plugging in one of the values into the slope equation.
  • #1
mathdad
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Find an equation of the line that passes through (6, -3) and has y-intercept 8.

The y-intercept 8 can be expressed as the point (0, 8).

Correct?

I then find the slope of (6, -3) and (0, 8).

Yes?

The next step is to plug one of the above points and the slope into the point-slope formula and solve for y.

Is any of this right?
 
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  • #2
RTCNTC said:
Find an equation of the line that passes through (6, -3) and has y-intercept 8.

The y-intercept 8 can be expressed as the point (0, 8).

Correct?

Correct.

RTCNTC said:
I then find the slope of (6, -3) and (0, 8).

Yes?

Yes.

RTCNTC said:
The next step is to plug one of the above points and the slope into the point-slope formula and solve for y.

An equation for a line is y = mx + b where m is slope and b is the y-intercept. To write the equation of your line in this form we need the slope and y-intercept. For the y-intercept, what does the fact that (0, 8) is on the line tell you when you substitute for x and y in your y = mx + b equation?
 
  • #3
greg1313 said:
Correct.
Yes.
An equation for a line is y = mx + b where m is slope and b is the y-intercept. To write the equation of your line in this form we need the slope and y-intercept. For the y-intercept, what does the fact that (0, 8) is on the line tell you when you substitute for x and y in your y = mx + b equation?

When I substitute (0,8) into y = mx + b, the answer is b = 8.
This means the graph crosses the y-axis at the point (0,8).
 
  • #4
(6,-3) & (0,8)

m = (8-(-3))/(0-6)

m = (8+3)/(-6)

m = -11/6

I will use (0,8).

y - 8 = (-11/6)(x - 0)

y - 8 = (-11x/6)

y = (-11x/6) + 8

Yes?
 
  • #5
We are given that the line has $y$-intercept 8, so your line may be written as:

\(\displaystyle y=mx+8\)

Now, we are given the point on the line $(6,-3)$, and so substituting for $x$ and $y$, we have:

\(\displaystyle -3=m(6)+8\)

Solving for $m$, we find:

\(\displaystyle m=-\frac{11}{6}\)

And so our line is:

\(\displaystyle y=-\frac{11}{6}x+8\)

This agrees with your result. (Yes)
 
  • #6
MarkFL said:
We are given that the line has $y$-intercept 8, so your line may be written as:

\(\displaystyle y=mx+8\)

Now, we are given the point on the line $(6,-3)$, and so substituting for $x$ and $y$, we have:

\(\displaystyle -3=m(6)+8\)

Solving for $m$, we find:

\(\displaystyle m=-\frac{11}{6}\)

And so our line is:

\(\displaystyle y=-\frac{11}{6}x+8\)

This agrees with your result. (Yes)

Always good to know more than one method. BTW, thank you for answering my PM questions. I will reply in full later today...
 

FAQ: I have a few more questions.No problem, happy to help!

What is the equation of a line?

The equation of a line is a mathematical expression that describes the relationship between two variables, typically represented as y and x. It has the form y = mx + b, where m is the slope of the line and b is the y-intercept, or the point where the line intersects the y-axis.

How do you find the slope of a line?

The slope of a line is found by dividing the change in y-coordinates by the change in x-coordinates between any two points on the line. This can be represented as (y2 - y1) / (x2 - x1), where (x1, y1) and (x2, y2) are coordinates of the two points. Alternatively, if the equation of the line is known, the slope can be found by identifying the coefficient of the x-term.

What is the y-intercept of a line?

The y-intercept of a line is the value of y when x is equal to 0. This can also be thought of as the point where the line crosses the y-axis. In the equation y = mx + b, b represents the y-intercept.

How do you graph a line using its equation?

To graph a line using its equation, you can plot the y-intercept, which is the point (0, b), on the y-axis. Then, using the slope (m), you can identify another point on the line by moving m units in the y-direction and 1 unit in the x-direction from the y-intercept. You can then connect these two points to create the line.

Can the equation of a line have more than one solution?

No, the equation of a line typically has one solution, which is the point where the line intersects the x-axis. However, if the equation is written in standard form (Ax + By = C), it can have an infinite number of solutions, as any point on the line will satisfy the equation.

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