Derivative formulas

[Ian McPherson]

I'm doing my final review, and I am haveing trouble with this question. "Find the derivative using formulas.
x^-4 + 2x -1 The given answer is -3x^-4+4x-1
x^-1

I tried simply moving the x^-1 up and getting x^-4 +3x -1, and finding the derivative. That wasn't right.
Then i tried using (x+h)^-4 + 2(x+h) -1 - (x^-4 + 2x - 1) all over h, however as soon as i distribute the - sign to the last part both the ones in the equation disappear and the x's cancel out leaving me only with ones. What do i need to do to reach the correct answer? thanks

 

[Ian McPherson]

found my problem. You don't add the x^1 that is moved up, you distribute it to all terms

 

[mmm4444bot]

Dividing by a fraction is the same as multiplying by its reciprocal.

That is why dividing by 1/x is the same as multiplying by x/1.

 

[michaela_n]

When finding the derivative of a fraction you use the quotient rule. So if you have f/g, you solve my doing (fⁱg)-(gⁱf)/g².