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Help me pls!

 Mar 27, 2021
 #1
avatar
+1

-5i^2 + 120 i = P     will be max at   i = -b/2a      where a = -5    b = 120

          max will be   at   i =  -120 / (2* (-5)) = 12 amps

 Mar 27, 2021
 #2
avatar+22006 
+1

Another way to get the answer:

 

To find the maximum, find the first derivative and set it equal to zero.

 

Problem:             P  =  120·i  -  5·i2

 

First derivative:  P'  =  120  -  10i

 

Setting the first derivative to zero:  120  -  10·i  =  0

                                                                  -10·i  =  -120

                                                                        i  =  12 amps

 Mar 27, 2021
 #3
avatar+315 
0

Oh that's why I got it wrong I forgot the sign for -120 I said 120 (ー_ー)

See that's how dumb I am today!

wolfiechan  Mar 27, 2021

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