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View Full Version : Check my algebra really quick :o


iamsmooth
Oct29-09, 03:12 AM
1. The problem statement, all variables and given/known data
y-\frac{9}{2}=\frac{16}{15}(x-4)



2. Relevant equations
y = mx+b?


3. The attempt at a solution

y-\frac{9}{2}=\frac{16}{15}(x-4)

15y-\frac{135}{2} = 16(x-4)

15y-\frac{135}{2} = 16x-64

30y-135=32x-128

30y-32x=7

The book says the answer is 32x + 30y = 263, which I can't get because of the negative sign. So either my algebra sucks, the given answer is wrong, or my original equation isn't right, but it should be since I'm given the points (4,\frac{9}{2}) and the slope is \frac{16}{15}.

Pengwuino
Oct29-09, 03:26 AM
Looks right, what was the original question?

iamsmooth
Oct29-09, 03:41 AM
Oh yup, I screwed up the equation. The original question is a derivative where I had to figure out the equations for the tangent and normals of a line. I got 15/16 for slope and to get the normal, I just inverted it to get 16/15, when a normal is actually -1/slope which makes it -16/15. So that one wrong sign messed everything up. I was doubting my algebra...

Anyways thanks a lot :D