O-Level Mathematics Directed Numbers Notes Zimbabwe

Study Mathematics notes on Directed Numbers for O-Level. Useful for revision, homework, and exam preparation in Zimbabwe.

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Exam board: ZIMSEC
Subject: Mathematics
Level: O-Level
Document: Notes
File: PDF, 3.9 MB

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This is the ZIMSEC O-Level Mathematics notes. It is a free notes for revision.

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DIRECTED NUMBERS

Qsm.
1. Evaluate
a. $\frac{-3+5}{-2(7+-4)}$
b. $(-4+-6)(3--2)$
c. $3-+3(-2-1)$

Sln
a. $\frac{-3+5}{-2(7+-4)}$
\[
\begin{array}{c}
=\frac{3}{-2(7-4)}
=\frac{3}{-2 \times 3}
=\frac{3}{-6}
=-\frac{1}{2}
\end{array}
\]
b. $(-4+-6)(3--2)$
\[
\begin{array}{c}
=(-4-6)(3+2)
=-10 \times 5
=-50
\end{array}
\]
c. $3-+3(-2-1)$
\[
\begin{array}{c}
=3-3(-5)
=3+15
=18
\end{array}
\]

Asn
2. Simplify as far as possible
\[
\frac{(-5+-4)-(2-+13)}{-2(3--1)}
\]
\[
\begin{array}{c}
=\frac{(-9)-(-11)}{-2(4)}
=\frac{-9+11}{-8}
=\frac{2}{-8}
=-\frac{1}{4}
\end{array}
\]

06n
3. Evaluate $\frac{(-3--5)-(-7--4)}{(-2--1)(-14--19)}$

Ans
\[
\frac{(-3--5)-(-7--4)}{(-2--1)(-14--19)}
\]
\[
=\frac{(-3+5)-(-7+4)}{(-2+1)(-14+19)}
\]
\[
=\frac{2--3}{-1 \times 5}
\]
\[
=\frac{5}{-5}
\]
\[
=-1
\]

Ans
\[
\begin{array}{l}
\frac{(-5+-4)-(2-+13)}{-2(3--1)}
=\frac{(-5-4)-(2-13)}{-2(3+1)}
\end{array}
\]

Dasn
4. Simplify as far as possible
a) $-2(7-+12)(-3--5)$
b) $\frac{(3--4)-(1-+2)+(-3-+1)}{-5-[(4-+7)+(-4--4)]}$

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