Two Equation Two Unknown: 6.6287=ax^3+bx^2, 0=3ax+2b

[terry33199]

i'm working on a word problem and just need a and b yet. I don't know how to solve for two unknowns.

i need to find a and b with these two equations:

6.6287 = ax^3 + bx^2
0 = 3ax + 2b

x = 64.515

i appreciate your help.

 

[o_O]

Try taking the derivative of the first equation. The derivative of 6.6287 will be 0 so you can set the first line's derivative and the second line equal to each other.

 

[terry33199]

I found a different way to do it. I solved for b in the second equation. Then I plugged that into the first equation and found a. Then I plugged a into the first equation and found b.

 

[pka]

I found a different way to do it. I solved for b in the second equation. Then I plugged that into the first equation and found a. Then I plugged a into the first equation and found b.

That is really the best way to do this problem.