Question 172963: Here's my problem I need some help!!! When you use y-y=m(x-x). I can do everything except for the final answer. Example: m=7/8,(2,-7)
I can set up the problem
y-(-7)=7/8(x-2)
y-(-7)=7/8x-7/4
This final step is where I have trouble and can't seem to understand.
They say to add -7 to 7/4, but how would you get an answer of 35/4?
Found 3 solutions by gonzo, solver91311, stanbon:
Answer by gonzo(654)   (Show Source):
You can put this solution on YOUR website! y = m*x = b
b is the y intercept (value of y when x = 0).
you have a point and a slope.
point is (x,y) = (2,-7)
slope is m = 7/8
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those are given.
you have m and you want to solve for b.
you take the point and you replace y with -7 and you replace x with 2.
your formula with 7/8 as m becomes:
y = (7/8)*x + b
your formula after you replace y with -7 and x with 2 becomes:
-7 = (7/8)*2 + b
you solve for b.
you multiply both sides of the equation by 8 to remove the denominator.
you get:
-7*8 = 8*((7/8)*2 + b)
which becomes
-56 = 8*(7/8)*2 + 8*b
which becomes:
-56 = 7*2 + 8*b
which becomes:
-56 = 14 + 8*b
you subtract 14 from both sides of the equation to get:
-56 -14 = 14 - 14 + 8*b
which becomes:
-70 = 8*b
you divide both sides of the equation by 8 to get:
-70/8 = 8*b/8
which becomes:
-70/8 = b
which becomes:
b = -35/4
your final equation becomes:
y = 7/8*x - 35/4
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if you graph the equation, you should be able to see that.
graph is shown below:
when x = 0, y should be -35/4
as you can see from the graph, it is (-8.75).
also when y = 0, x should be 10 which you can also see from the graph.
look below the graph for further comments:
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tracing back what you did:
m=7/8,(2,-7)
you set up the problem as:
y-(-7)=7/8(x-2)
y-(-7)=7/8x-7/4
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you used the form: (y-y1) = m*(x-x1) which is good.
m is 7/8 which is good.
y1 is -7 which is good.
x1 is 2 which is good.
formula becomes:
y-(-7) = (7/8)*(x-2) which you got ok.
you seem to also have gotten the next step ok:
y-(-7) = (7/8)*x - ((7/8)*2)
which became:
y-(-7) = (7/8)*x - (7/4)
so you did ok up until the time you stopped.
the next step was to remove the parentheses.
y+7 = (7/8)*x - (7/4)
the next step was to subtract 7 from both sides of the equation to move it from the left side to the right side.
y + 7 - 7 = (7/8)*x - (7/4) - 7
simplifying, 7 on the left cancels out.
y = (7/8)*x - (7/4) - 7.
you can multiply both sides of the equation to remove the denominators to get:
8*y = 8*(7/8)*x - 8*(7/4) - 8*7
which becomes:
8*y = 7*x - 2*7 - 8*7
which becomes:
8*y = 7*x - 14 - 56
which becomes:
8*y = 7*x - 70
you can then divide both sides of the equation by 8 to get only 1*y on the left side only.
you get:
8*y/8 = 7*x/8 - 70/8
which becomes:
y = (7/8)*x - (70/8)
which becomes:
y = (7/8)*x - (35/4)
after you simplify (70/8) by dividing numerator and denominator by 2.
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Answer by solver91311(24713)  (Show Source):
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! I can set up the problem
y-(-7)=(7/8)(x-2)
y-(-7)=7/8x-7/4
This final step is where I have trouble and can't seem to understand.
They say to add -7 to 7/4, but how would you get an answer of 35/4?
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You get:
y+7 = (7/8)x - (7/4)
y = (7/8)x - (7/4) - (28/4)
y = (7/8)x - (35/4)
=========================
Cheers,
Stan H.
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