# Eliminate the parameter

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• Feb 8th 2007, 11:28 AM
kcsteven
Eliminate the parameter
I am stuck and need a push. This problem looks simple, I have done quite a few of these but this one is a little different, it's giving me trouble. I am suppose to eliminate the parameter t to find a cartesian equation for:
x = t^2
y = 7 +1t
x = Ay^2 + By + C

Where:
A =
B =
C =
I was trying to solve for t as a function of Y and I thought I had it but no cigar. I am sure it is just that I have been sitting down for an hour and I need to walk away and come back to this because it seems to be easy but I just CAN'T!!!! Please HELP!
Thank you,
Keith Stevens:eek:
• Feb 8th 2007, 12:36 PM
Ramanujan
Hint
Hey Keith. Try finding an expression for Y in terms of t, so you can substitute that into X = t^2.
• Feb 9th 2007, 02:54 AM
chogo
so what you need to do is first use equation (2)

$y = 7 + 1t$ -> therefore t is $y - 7 = t$

then you substitute this into equation (1)

$x = (y-7)^2$

then equate this value of x to equation (3). They are bothe quadratic so compare the coefficients.

$(y-7)^2 = Ay^2 + By + C$

$y^2 - 14y + 49 = Ay^2 + By + C$

compare the coefficients

a = 1
b = -14
c = 49