Question
Function
x′(n)=12δun2
Evaluate
x(n)=δn2×2n(un−u(n−2))
Simplify
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Evaluate
δn2×2n(un−u(n−2))
Subtract the terms
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Simplify
un−u(n−2)
Expand the expression
un−un+2u
The sum of two opposites equals 0
0+2u
Remove 0
2u
δn2×2n×2u
Multiply the terms with the same base by adding their exponents
δn2+1×2×2u
Add the numbers
δn3×2×2u
Multiply the terms
δn3×4u
Use the commutative property to reorder the terms
4δn3u
x(n)=4δn3u
Evaluate
x(n)=4δun3
Take the derivative of both sides
x′(n)=dnd(4δun3)
Use differentiation rule dxd(cf(x))=c×dxd(f(x))
x′(n)=4δu×dnd(n3)
Use dxdxn=nxn−1 to find derivative
x′(n)=4δu×3n2
Solution
x′(n)=12δun2
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