LESSON NOTES ON CALCULATING THE VALUE OF ALGEBRAIC EXPRESSIONS

                             LESSON NOTES ON CALCULATING THE VALUE OF ALGEBRAIC EXPRESSIONS

SUBJECT: Algebra

TOPIC: Algebraic  Expressions

LESSON: Calculating the numerical value of an algebraic expression

PREVIOUS KNOWLEDGE:Students can add, subtract, multiply ,divide two or more linear algebraic expressions

TEACHING AIDS: A cardboard paper with some algebraic expressions written on.

OBJECTIVES: By the end of the lesson, students are expected to replace variable with numbers in algebraic expressions and evaluate them.

TEACHING METHODS:demonstration, group discussion, questioning and assignment.

GRADE LEVEL: 7

DURATION: 40 minutes

INTRODUCTION:

i)                    Simplify 2x+4x-3

ii)                   Calculate the value of 7x+3 when x=2.

                  SOLUTION

i)                    2x+4x-3= 6x-3.answer

ii)                   7x+3=7(2)+3

7x+3=14+3

7x+3=17.  Answer

PRESENTATION:

-To calculate the value of an algebraic expression, replace the variable(s) in the expression by numbers that stand for the variable(s) then simplify your result.

 ^{Example 1: Calculate the value of each of the following expressions by substituting the variables in each}

^{i)                                         2x+3,  when x=2}

^{ii)                                      4x-b, when x=1 and  b=3}

ⁱⁱⁱ⁾                                   Y², when y=2

iv)               x²+1 , when x=3

v)                 3a³-2

   4       , when a=2

                       SOLUTION

i)                    2x+3,  x=2

2x+3=2(2)+3

2x+3=4+3

2x+3=7.answer

ii)                   4x-b, x=1 , b=3

4x-b=4(1)-3

4x-b=4-3

4x-b=1.answer

iii)                 Y², y=2

Y²=y×y

Y²=2×2

Y²=4.answer

iv)                 2x²+1, x=3

2(x)(x)+1=2(3)(3)+1

2(x)(x)+1=18+1

2x²+1=19.answer

v)                  3a³-2

    4        ,a=2

3a³-2 =3(a)(a)(a)-2

    4             4

          =3(2)(2)(2)-2

                   4

          =24-2

               4

3a³-2 =22

    4       4. answer.

EXAMPLE 2: Calculate the value of each of the follwing expressions, simplifying your  answers as far as possible

i)                    PRT  ; p=4, R=5,T=2

100

ii)                   P(1+r )  ;P=2, r=50

        10

                    SOLUTION.

i)                    PRT =4×5×2

100     100

PRT=40

100  100

PRT=4

100  10 

PRT=2

100   5. Answer.

ii)                   P(1+r   )= 2(1+ 50 )

        10               10

P(1+ r )=2(1+5)

        10

P(1+r )=2(6)

        10

P(1+r )=12. Answer.

       10

                      EVALUATION

Calculate the value of each of the following expressions by substituting the numbers given beside each.

i)                    4y-3x; y=3, x=2

ii)                   3x-3m;  x=2, m=4

2

iii)                 P-K ; p=1, k=2

    6

iv)                 n(2a+(n-1)d) ; n=2, a=1, d=5

2

SUMMARY

To calculate the numerical value of a linear expression, replace the variable by any given number and simplify your result.

                    CONCLUSION.

Assignment.

Calculate the value of each of the following expressions simplifying your result as far as possible.

i)                    6x+3y; x=2, y=5

ii)                   2m-3n ; m=4 ,n=-2

iii)                 1πr²h ; π=22 , r=3, h=10.

     3               


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