Page 82 - Mathematics_F1

Simplify each of the following algebraic expressions:
2. 12m + 13m 6. 3k – 18k + 15k 10. r + 2r + 3r + 4

3. 5y + 7y – 4y 7. 15n – 9n 11. 8y – 3 – 7y + 4
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4. 9z + 6z – 8z + 5z 8. x + 4 – 5x Tanzania Institute of Education

5. 24w – 28w 9. 4k – k + 3k

Find the value of each of the following algebraic expressions:
12. 6n + 8m + 4n – 5m, if m = – 3 and n = 4

13. 14x + 8 – 3x + 2, if x = – 2

14. 26 + 2b – 6c – 3b + 6c, if c = 5 and b = – 4
15. 3a – 5b – 7a + 6c + 7a, if a = 3, b = 2, and c = 5

16. 5a – b – a + 9b + 3a, if a = 4 and b = –2
17. 4x – 6y + 7x + 2y, if x = 10 and y = – 2
18. 9y + 5 – 4y + 3x + 2, if x = 4 and y = – 4

19. 13x + 14 + 8x – 4 – 11x, if x = – 6

20. 7x + 3y – 4 – 3y, if x = 5 and y = – 3
21. 8m + 0.4m – 2 – 6m + 8, if m = – 4

22. 4 x y − 6 k l + 10x y − 4k l , given that x = 1, y = 2, k = –2, and l = –3
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Multiplication and division of algebraic expressions
Just as 2 × 3 = 3 × 2, so is n × m = m × n and a × b = b × a = ab = ba.
Therefore, to multiply 3n by 5 is the same as to multiply 5 by 3n.

That is, 3n × 5 = 5 × 3n = 15 × n = 15n.

Similarly, 3n × 5m = 3 × n × 5 × m
Mathematics Form One
= 3 × 5 × n × m

= 15 × n × m

= 15mn.
Thus, 3n × 5m = 15mn.

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