1. ## tangents

i have two tangents that i have the equations to. the question asks to find the co-ordinates were the two tangents intersect. i am guessing that i will have use the two tangent equations in a similtaneous equation but i dont know how can some one help me ? the two equations are Y=5x-90 at x=5 and y=-16x-2024 at x=6

2. equal your equations to each

$\displaystyle 5x - 90 = -16x -2024$

$\displaystyle 21x = -1934$

$\displaystyle x = \frac{-1934}{21}$

so now just plug in x into one of your original equations and it will give you your y

If you have any questions feel free to ask.

3. im still having trouble with it im getting an y value of -550.47 this is far to great to be real on my graph i think the problem lies in thi equation y=-16x-2024
my dy/dx was 3x^2-12x-31 ax was 6 could some one see if they got the same answer as me

4. What was the original function before you took the derivative and what was the original question you were working on?

5. x^3-6x^2-31x+120 was the original function the question was to take a point one with a posotive gradient and one with a negative gradient on the cubic that i found from the equation x^3-6x^2-31x+120 and draw a tangent i then had to work out the tangent equation. i then had to extend the tangents until they intersect and find the co-ordinate at which they intersect