question core 3

Given that y=(3x-7)^5 +5(3x-7)^4, show that dy/dx=45(3x-7)^3(x-1)

When i differentiated the original equation, i got:
dy/dx=15(3x-7)^4 + 60(3x-7)^3
I assume i have to simply this but i'm unsure how. So far, i have tried making dy/dx=0 and taking away 60(3x-7)^3, but this doesn't seem to work?

Reply 1

Kevin De Bruyne

21

Original post by Chelsea12345

Given that y=(3x-7)^5 +5(3x-7)^4, show that dy/dx=45(3x-7)^3(x-1)

When i differentiated the original equation, i got:
dy/dx=15(3x-7)^4 + 60(3x-7)^3
I assume i have to simply this but i'm unsure how. So far, i have tried making dy/dx=0 and taking away 60(3x-7)^3, but this doesn't seem to work?

Although it is good that you have tried something (seriously, not in a patronising way) setting the equation to 0 isn't justified by any info given in the question.

Notice that a + b has turned into one term - which would be your hint that the question wants you to f _ _ _ _ _ _ _ e and then simplify it.

(edited 6 years ago)

Reply 2

Chelsea12345

OP

12

Original post by Kevin De Bruyne

Although it is good that you have tried something (seriously, not in a patronising way) setting the equation to 0 isn't justified by any info given in the question.

Notice that a + b has turned into one term - which would be your hint that the question wants you to f _ _ _ _ _ _ _ e and then simplify it.

is there meant to be a space there? or is the word not appearing?

Reply 3

the bear

20

Original post by Chelsea12345

is there meant to be a space there? or is the word not appearing?

he is trying not to give you too much help:

F _ _ _ O _ _ _ E

Original post by the bear

he is trying not to give you too much help:

F _ _ _ O _ _ _ E

Is there a C in there? :beard:

Reply 5

the bear

20

Original post by RDKGames

Is there a C in there? :beard:

F _ C _ O _ _ _ E

next !!

OP

U?

Original post by Chelsea12345

Given that y=(3x-7)^5 +5(3x-7)^4, show that dy/dx=45(3x-7)^3(x-1)

When i differentiated the original equation, i got:
dy/dx=15(3x-7)^4 + 60(3x-7)^3
I assume i have to simply this but i'm unsure how. So far, i have tried making dy/dx=0 and taking away 60(3x-7)^3, but this doesn't seem to work?