Because I just solved (2x+5)/x^2 and a derivative calculator is telling me the answer is -2(x-5) / x^3. Why didn't I have to chain on the derivative of the numerator?
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The derivative calculator is wrong.
Quotient Rule:
d/dx[ (2x + 5)/x^2 ]
(2x^2 - 2x(2x + 5)) / x^4
(2x^2 - 4x^2 - 10x) / x^4
(-2x - 10)/x^3
-2(x + 5)/x^3
It seems it should be +5 not -5
I'll also do it using the Product Rule:
d/dx[ (2x + 5)x^-2 ]
2x^-2 - 2(2x + 5)x^-3
2/x^2 - (4x + 10)/x^3
Now to get it to look like the quotient rule answer:
2x/x^3 - (4x + 10)/x^3
(2x - 4x - 10)/x^3
-2(x + 5)/x^3
Quotient Rule:
d/dx[ (2x + 5)/x^2 ]
(2x^2 - 2x(2x + 5)) / x^4
(2x^2 - 4x^2 - 10x) / x^4
(-2x - 10)/x^3
-2(x + 5)/x^3
It seems it should be +5 not -5
I'll also do it using the Product Rule:
d/dx[ (2x + 5)x^-2 ]
2x^-2 - 2(2x + 5)x^-3
2/x^2 - (4x + 10)/x^3
Now to get it to look like the quotient rule answer:
2x/x^3 - (4x + 10)/x^3
(2x - 4x - 10)/x^3
-2(x + 5)/x^3