- #1
fk378
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Homework Statement
Find a function f such that f'(x)=x^3 and the line x+y=0 is tangent to the graph of f.
Homework Equations
antiderative
The Attempt at a Solution
f(x)=(x^4)/4 + C
I don't know where to go from here... the tangent line equation is a way to find the slope, no? So rearranging x+y=0 gives y=x which means that the slope is 1...but wait, doesn't y=x mean that the tangent is a straight line, so therefore the derivative is 0? As you can tell, I'm very confused!