SOLUTION: Can anyone help with this? A line passes through the point (-4,-9) and has a slope of -3 . Write an equation for this line in x,y -coordinates.

Algebra ->  Graphs -> SOLUTION: Can anyone help with this? A line passes through the point (-4,-9) and has a slope of -3 . Write an equation for this line in x,y -coordinates.       Log On


   

Question 43077: Can anyone help with this?
A line passes through the point (-4,-9) and has a slope of -3 . Write an equation for this line in x,y -coordinates.

Found 2 solutions by Nate, prabhjyot:
Answer by Nate(3500) About Me  (Show Source):
You can put this solution on YOUR website!
Use point-slope form:
y+-+y1+=+m%28x+-+x1%29
y+%2B+9+=+-3%28x+%2B+4%29
y+%2B+9+=+-3x+-+12
y+=+-3x+-+21
+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+-3x+-+21%2C+-9%29+

Answer by prabhjyot(165) About Me  (Show Source):
You can put this solution on YOUR website!
Given slope m=-3
(x,y)=(-4,-9)
In the slope-intercept form of a straight line, we have y, m, x, and b. So the only thing we don't have a value for is b (which gives the y-intercept). Then all we need to do is plug in my slope and the x and y from this particular point, and then solve for b:
y = mx + b
-9=-3(-4)+b
-9=12+b
b=-21
Then the line equation must be y= -3x-21
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