Step-5

Title: Differentiation

Grade: 10-a Lesson: S2-L5

Explanation: Hello Students, time to practice and review the steps for the problem.

Lesson Steps

Step Type Explanation Answer

1

Problem

Find the derivative of the function \$"f"("x") = ("x"^2 + 1)^("x"^3 - 2"x")\$.

2

Step

The given function

\$"f"("x") = ("x"^2 + 1)^("x"^3 - 2"x")\$

3

Formula:

The power rule formula:

\$ "d"/"dx" "x"^"n" = "n" "x"^("n" - 1) \$

4

Step

Now we can use the chain rule to find the derivative of f(x), then simplify.

\$"d"/"dx" "f"("x") = "d"/"dx" (("x"^2 + 1)^("x"^3 - 2"x"))\$

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x" - 1) times "d"/"dx" ("x"^2 + 1) \$

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x" -1) times ("d"/"dx" "x"^2 + "d"/"dx"1) \$

5

Step

After differentiation

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + "1")^("x"^3 - 2"x" - 1) times (2"x" + 0) \$

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x" - 1) times (2"x") \$

6

Step

Therefore, the derivative of f(x) is \$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x" - 1) times (2"x")\$.

7

Choice.A

This option introduces the logarithmic term and subtracts instead of multiplying, making it incorrect

\$(2"x"^4 - 3"x"^3 + 3"x"^2"ln"("x"^2 + 1) + "x"^2"ln"("x"^2 + 1) + 2"ln"("x"^2 + 1))(("x"^2 + 1)^("x"^3 - 2"x" - 1)) \$

8

Choice.B

Option B arrives at the correct outcome despite not explicitly presenting the 2x factor. This is achieved through implicit differentiation within the composite term

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x" - 1) times (2"x")\$

9

Choice.C

This option factors out 2x, but it misses a key multiplication within the composite term, leading to an incorrect application of the power rule

\$ "f"'("x") = ("x"^3 - 2"x") ("x"^2 + 1)^("x"^3 - 2"x") times (2"x")\$.

10

Choice.D

This option shares the error of introducing \$ln(x^2 - 1)\$ and subtracting a term, making it incorrect

\$ (2"x"^4 - 6"x"^2 - 3"x"^4"ln"("x"^2 + 1) - "x"^2"ln"("x"^2 + 1) + 2"ln"("x"^2 + 1))(("x"^2 + 1)^("x"^3 + 2"x" + 1)) \$

11

Answer

Option

B

12

Sumup

Can you summarize what you’ve understood in the above steps?


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