Competition - post a photo you've taken of nature >>

Dy/dx again!

Farmerjj

What is dy/dx of (x^2+2x)/x^2 ?

Cheers

Scroll to see replies

Reply 1

16Characters....

Original post by Farmerjj

What is dy/dx of (x^2+2x)/x^2 ?

Cheers

Use the quotient rule:

\frac{d}{dx}\left( \frac{u(x)}{v(x)}\right) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2}

EDIT: Actually you could instead cancel common factors and split up into two fractions and then just differentiate as normal, no need for the quotient rule.

(edited 8 years ago)

Reply 2

Muttley79

Original post by Farmerjj

What is dy/dx of (x^2+2x)/x^2 ?

Cheers

What have you tried so far?

Is this for C1?

Reply 3

Farmerjj

Original post by Muttley79

What have you tried so far?

Is this for C1?

Yeah for C1

I'm not really sure how to approach it

Sinplify the indexes

Original post by 16Characters....

Use the quotient rule:

\frac{d}{dx}\left( \frac{u(x)}{v(x)}\right) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2}

EDIT: Actually you could instead cancel common factors and split up into two fractions and then just differentiate as normal, no need for the quotient rule.

when u do so much STEP u forget the basics #strugglez

(edited 8 years ago)

Reply 6

Farmerjj

Original post by 16Characters....

Use the quotient rule:

\frac{d}{dx}\left( \frac{u(x)}{v(x)}\right) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2}

EDIT: Actually you could instead cancel common factors and split up into two fractions and then just differentiate as normal, no need for the quotient rule.

So it's x^2/x^2 + 2x/x^2 and then what?

Reply 7

Muttley79

Original post by Farmerjj

Yeah for C1

I'm not really sure how to approach it

For C1 you need to divide the numerator by the denominator so your expression has no fractions.

Reply 8

Slowbro93

Original post by Farmerjj

So it's x^2/x^2 + 2x/x^2 and then what?

Do you have any of your own working out?

Reply 9

Muttley79

Original post by Farmerjj

So it's x^2/x^2 + 2x/x^2 and then what?

This is NOT in C1 - ignore it!

Reply 10

16Characters....

Original post by Farmerjj

So it's x^2/x^2 + 2x/x^2 and then what?

Simplify those two fractions by cancelling the common factors in the numerators and denominators and then use the usual rule for differentiating powers of x. (You may find it helpful to rewrite one of the fractions as x to a negative power after simplifying).

Reply 11

ubisoft

Original post by Farmerjj

So it's x^2/x^2 + 2x/x^2 and then what?

When you divide and the base is the same, you just subtract the powers

Reply 12

Muttley79

Original post by 16Characters....

Use the quotient rule:

\frac{d}{dx}\left( \frac{u(x)}{v(x)}\right) = \frac{u'(x)v(x) - u(x)v'(x)}{(v(x))^2}

EDIT: Actually you could instead cancel common factors and split up into two fractions and then just differentiate as normal, no need for the quotient rule.

Quotient rule is NOT in C1 don't confuse people!

Reply 13

Muttley79

Original post by 16Characters....

I think you need to stop posting wrong things - we never CANCEL in mathematics - we simplify expressions.

Reply 14

ubisoft

Original post by Muttley79

I think you need to stop posting wrong things - we never CANCEL in mathematics - we simplify expressions.

Lmfaooo what are you on about :rofl:

Reply 15

kkboyk

Original post by Farmerjj

Yeah for C1

I'm not really sure how to approach it

Split each into fraction, and use rule of indices e.g. (x^3)/(x^2) = x^1 (you just minus the power when dividing if they have the same base) and then differentiate normally

Reply 16

Farmerjj

Original post by Muttley79

I think you need to stop posting wrong things - we never CANCEL in mathematics - we simplify expressions.

Okay so would the answer be -2x^-2?

Reply 17

Muttley79

Original post by ubisoft

Lmfaooo what are you on about :rofl:

Ubisoft - real mathematicians NEVER talk about cancelling - that is not what we are doing.

We look for common factors and simplify - if you don't understand that you should not be offering help.

Reply 18

Muttley79

Original post by Farmerjj

Okay so would the answer be -2x^-2?

Yes but write it back as a fraction as it was given as a fraction.

Sorry about all the posters giving poor advice :frown:

Reply 19

ubisoft

Original post by Muttley79

Ubisoft - real mathematicians NEVER talk about cancelling - that is not what we are doing.

We look for common factors and simplify - if you don't understand that you should not be offering help.