Page 67 - Mathematics_Form_Two

Algebra

(b) How changing the number of Example 4�3

apples or oranges affects the total Given that x y = 4x + 6y, find the value
*
fruit count? of 6 4.
*
2. If an apple is sold at TShs 950 and an Solution
FOR ONLINE READING ONLY
orange is sold for Tshs 200, calculate Given x y = 4x + 6y. It follows that,
*
the total cost of buying all the fruits.
*
6 4 = (4 × 6) + (6 × 4)
= 24 + 24
= 48
Example 4�1 Therefore, 6 4 = 48. Mathematics for Secondary Schools
*
If a b = 5a – b, find the value of 6 9.
*
*
Example 4�4
Solution
2
2
*
From a b = 5a – b, it implies that, Given that p q = p – q , find the value
*
of 7 3.
6 9 = 5 × 6 – 9 *
*
= 30 – 9 Solution 2 2
*
= 21 From p q = p – q , it follows that,
2
7 3 = 7 – 3 2
*
Therefore, 6 9 = 21.
*
= 49 – 9
= 40
Example 4�2
Therefore, 7 3 = 40.
*
If a b = a – b, find the value of y given
2
*
that 4 (2 y) = 4. Example 4�5
*
*
Solution If * 3a + find the value of 5 8.∗
,find 5 8.
b
ab =
*
2
Given a b = a – b.
*
Start with the operation in the brackets. Solution
,find 5 8.
*
*
4 (2 y) = 4 (2 – y) Given ab = 3a + b. It follows that,
2
*
*
*
5 * 8 = (3 × 5) + 8
= 4 (4 – y) = 15 + 8
*
= 4 – (4 – y)
2
= 23
= 16 – 4 + y Therefore, 5 * 8 = 23.
= 12 + y
Thus, 12 + y = 4 Example 4�6
x
** value of
y = –8 If x y = + 3 , find 5 (8 6).y find the
*
Therefore, y = –8. 5(86).∗ ∗
61
Student's Book Form Two
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MATHEMATIC F2 v5.indd 61 11/10/2024 20:11:47
MATHEMATIC F2 v5.indd 61