# Cambridge Prelim MX1 Textbook Marathon/Q&A

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• 12 Jun 2017, 5:45 PM
a_t
Re: Cambridge Prelim MX1 Textbook Marathon/Q&A
Need help with this please. Q2A of Ex 7B
For each function below, simplify f(x + h) − f(x) / h , then take lim h→0 to find the derivative.

(a) f(x) = 5x + 1
• 12 Jun 2017, 5:53 PM
1729
Re: Cambridge Prelim MX1 Textbook Marathon/Q&A
Quote:

Originally Posted by a_t
Need help with this please. Q2A of Ex 7B
For each function below, simplify f(x + h) − f(x) / h , then take lim h→0 to find the derivative.

(a) f(x) = 5x + 1

\noindent \begin{align*}\frac{f(x+h) - f(x)}{h} &= \frac{[5(x+h) + 1] - (5x+1)}{h} \\ &= \frac{5x + 5h + 1 - 5x - 1}{h} \\ &= \frac{5h}{h} \\ &= 5 \end{align*} \\ And so f'(x) = \lim_{h \rightarrow 0}\frac{f(x+h) - f(x)}{h} = \lim_{h \rightarrow 0}5 = 5 \\ ie. f'(x) = 5.
• 15 Jun 2017, 6:12 PM
joelle_kk
Re: Cambridge Prelim MX1 Textbook Marathon/Q&A
Need Help!!! 2H 16a & b
Three tourists T1, T2 and T3 at ground level are observing a landmark L. T1 is due north of L, T3 is due east of L, and T2 is on the line of sight from T1 and T3 and between them. The angles of elevation to the top of L from T1, T2 and T3 are 25', 32' and 36' respectively.

a) show tan angle LT1T2 = cot 36 / cot 25
b) use the sine rule in triangle LT1T2 to find, correct to the nearest minute, the bearing of T2 from L
• 19 Jun 2018, 4:57 AM
Pakka
Re: Cambridge Prelim MX1 Textbook Marathon/Q&A
Attachment 34573
Pls provide full working. Thanks
• 19 Jun 2018, 10:57 AM
Drongoski
Re: Cambridge Prelim MX1 Textbook Marathon/Q&A
Quote:

Originally Posted by Pakka
Attachment 34573
Pls provide full working. Thanks

Use change of base formula:

$log _{ab} x = \frac {log _a x}{log _a (ab)} = \frac {log _a x}{log _a a + log _a b} = \frac {log _a x}{1 + log _a b}$
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