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# Finding constant Watch

1. The graph of y=2x+k meets the grpah of y=x^2 +3x -18 at only one point. Find the vlaue of the constant K.

So as it only meets at one point the discriminant is going to be eqaul to 0 as it will be a tangent to the curve, but im not too sure what to do. I think im overthinking it
2. (Original post by hazbaz)
The graph of y=2x+k meets the grpah of y=x^2 +3x -18 at only one point. Find the vlaue of the constant K.

So as it only meets at one point the discriminant is going to be eqaul to 0 as it will be a tangent to the curve, but im not too sure what to do. I think im overthinking it
Set the equations set to each other to eliminate y.

Rearrange the quadratic so it is equal to zero.

NOW find the discriminant and set it equal to zero.
3. has one real root.
has one real root.

expand and solve for k
4. Ah ok i was almost right i just didnt use the discriminant when i rearranged the quadratic =/ Thank you

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Updated: December 1, 2010
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