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Differentiating functions: Find the error

Problem

Wang Fang tried to find the derivative of x53x+9. Here is her work:
Step 1: This is the quotient of x5 and 3x+9. So we should use the quotient rule.
Step 2:
ddx[x53x+9]=ddx[x5]ddx[3x+9]
Step 3: Finding the derivatives of the factors:
ddx[x5]=5x4ddx[3x+9]=3
Step 4: Putting it all together:
=ddx[x53x+9]=ddx[x5]ddx[3x+9]=5x43
Is Wang Fang's work correct? If not, what's her mistake?
Choose 1 answer:
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