Thread: multiple unknowns!!

Hi I am have troubles solving for a and b.

Sections 1,2 and 3 all join and are continuous. At points B and C the gradient at the end of one function is the same as the gradient at the beginning of the next.

For section 1, i.e. A to B, y=0.01x^2-1.2x+50
For section 2, i.e. B to C, y=ax^2+bx-250
For section 3, i.e. C to D, y=cx^2+dx+605

Point A is ( 0,e=50 )
Point B is ( 100,f=30)
Point C is ( 150,g )
Point D is ( h,0 )

I found e=50 and f =30.

I cant solve for the other unknowns??

I believe there is something wrong with the problem statement.

Consider the segments A--> B and B--> C. You state that the functions for the two segments must be equal at point B AND the derivatives of the functions must be equal at point B. Setting the derivatives equal, gives a=0.01 and b = -1.2, which does not result in the functions being equal.

Yes, and [tex]f= .01(100)^2- 1.2(100)+ 50= 30. Also, y'= 2(.01)(100)+ 1.2= 3.2.

At point B, x= 100 so you want and .
From those two equations, you can solve for a and b.

At point C, x= 150 so you want and .

Since you now know a and b, you should be able to solve for c and d.