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Let $f(x)=\begin{cases}\max\{|x|,x^2\},&|x|\le2\\8-2|x|,&2<|x|\le4\end{cases}$. Let $S$ be the set of points in $(-4,4)$ where $f$ is not differentiable. Find $S$.
On $[-2,2]$: $\max(|x|,x^2)=x^2$ when $x^2\ge|x|$, i.e., $|x|\ge1$; equals $|x|$ when $|x|\le1$.
So $f(x)=|x|$ for $|x|\le1$ and $f(x)=x^2$ for $1\le|x|\le2$.
Check non-differentiability: At $x=0$: $|x|$ is not differentiable. At $x=\pm1$: left-hand $f'=\pm1$, right-hand $f'=2x=\pm2$ — not equal, so not differentiable. At $x=\pm2$: $f(2^-)=4$, $f(2^+)=4$; $f'(2^-)=4$, $f'(2^+)=-2$ — not differentiable.
So $S=\{-2,-1,0,1,2\}$.
Compare the two quantities below.
Column A: $9^7$
Column B: $10{,}000{,}000$
Note that $10{,}000{,}000 = 10^7$.
Comparing $9^7$ vs $10^7$: since the base $9 < 10$ and both exponents are equal and positive, we have $9^7 < 10^7$.
Therefore Column B ($10^7$) is greater than Column A ($9^7$).
Correct SI unit pair:
Power: watt (J/s). Energy: joule; Force: newton; Velocity: m/s.
Iga suspects that some credit notes received from suppliers have not been recorded. Which of the following actions should she take to verify this?
- Compare purchases ledger balances against supplier statements
- Extract a trial balance of individual purchases ledger accounts
- Prepare a purchases ledger control account
Comparing the business's records with the supplier's statement is the most effective way to find missing credit notes, as the supplier will have recorded the credit note even if the business forgot to. A trial balance or control account only checks internal consistency.
Given that $x \neq 0$, compare the two quantities below.
Column A: $\dfrac{x}{|x|}$
Column B: $1$
The expression $\dfrac{x}{|x|}$ is the sign function of $x$:
- If $x > 0$: $\dfrac{x}{|x|} = \dfrac{x}{x} = 1$ → equal to Column B
- If $x < 0$: $\dfrac{x}{|x|} = \dfrac{x}{-x} = -1$ → less than Column B
Since $x$ can be positive or negative, and we get different results, the relationship cannot be determined from the information given.
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