buksis-4.2 revisi akhir

8/14/2019 BUKSIS-4.2 REVISI AKHIR

http://slidepdf.com/reader/full/buksis-42-revisi-akhir 1/6

at are you going to learn? To define a linea r

eq uation with one

variable

To m ake a mo de l to

state an eq uation

To understa nd Solution

and Solution Set

Key Terms : • equation

• linea r eq ua tion with

one variab le

• solution and Set

solution

Think and discuss. A circus has 3 male and 3 female

tigers. a) If the keeper feeds 39 kg of meat to the tigers

each day and each tiger gets the same portion, what

is the weight of meat fed to each tiger everyday?

Think and discuss. A circus has 3 male and 3 female

tigers. a) If the keeper feeds 39 kg of meat to the tigers

each day and each tiger gets the same portion, what

is the weight of meat fed to each tiger everyday?

b) If each tiger eats m kg of meat everyday, and the

meat eaten by all tigers is 45 kg, write down an open

sentence related to the weight of meat eaten by all

tigers. How many kg of meat are eaten by six female

tigers?

b) If each tiger eats m kg of meat everyday, and the

meat eaten by all tigers is 45 kg, write down an open

sentence related to the weight of meat eaten by all

tigers. How many kg of meat are eaten by six female

tigers?

c) If a male tiger eats meat twice as much as a female

tiger, and the meat eaten by all tigers is 36 kg, how

many kilograms of meat are eaten by six male tigers?

c) If a male tiger eats meat twice as much as a female

tiger, and the meat eaten by all tigers is 36 kg, how

many kilograms of meat are eaten by six male tigers?

44..22

Picture 4..4

In the tiger problems:

• If one tiger eats m kg, then the relation is 6m = 45.

• The value of m is unknown. Therefore, m is a variable. An open sentencethat uses the sign “=” is called an equation.

• If the highest power of the variable in an equation is 1, then thatequation is called a linear equation.

Mathematics for Junior High School – Year 7/ 131



Consider the following equations. Determine which

ones are linear equations with one variable? Give the

reasons.

a) p - 12 = 5

b) t + r = 28

c) h2 = 16

d) 2k – 3 = k + 7

Think and discuss. To celebrate the Independence

Day of Indonesia, students of “SMP Association” and

students of “SMP Reconciliation” held a competition

in the square of the district. They went to the square

of the district by car and bicycle. Students of “SMP

Association” needed three cars and six bicycles.

Students of “SMP Reconciliation” needed two cars

and seven bicycles.

The number of students in each car was the same.

If the total number of the students of those two

schools was 88,

(a) how many cars were used to go to the square of

the district?

(b) how many students went to the square of the

district by bicycle?

(c) how many students were there in each car?

Look at the tiger problem again.

The equation we get is 6m = 45. If m is substituted by

five, then the sentence becomes 6 x 5 = 45 and it is

132 / Student’s Book – Linear Equations and Inequalities with One Variable



false.

If m is substituted by 6, then the sentence becomes 6 x

6 = 45 and it is false.

If m is substituted by 7, then the sentence becomes 6 x

7 = 45 and it is false.

2

1If m is substituted by 7 , then the sentence becomes

6 x 72

1 = 45 and it is true. Is there any value of m to

make the sentence true?

The value to make the equation becomes true is

called a solution of the equation. Therefore, the

solution of the equation 6m = 45 is 72

1 .




1. In the following sentences, determine which one

is a linear equation with one variable and which one

is a non linear equation with one variable. Give

reason.

a. 3s = 4 – s f. x2 – x = 0

b. –5t > t + 2 g. k ³ -5k +3

c. m = 2n – 5 h. x – y = 7

d. x = 9 – 3x i. 2s + s + 9

e. y + 5 = -1 j. 5m = 2m + 5

2. Write T in the bracket if the statement is true and

write F if the statement is false (do it by replacing the

value of x in the equation).

a. 4 is a solution of –2x + 4 = x (. . . )

b. –3 is not a solution of 2x – 3 = 9 ( . . . )

c. 5 is a solution of 5x – 10 = x + 10 ( . . . )

d. 0 is a solution of x – 3 = 2x – 3 ( . . . )

e. –1 is not a solution of 3x + 3 = 0 ( . . . )

4

3is a solution of 4x – 5 = 8x + 1 ( . . . )f.

5

3is a solution of 5x + 6 = -10x – 3 ( . . . ) g. -

3. Write examples of open sentences that can be

represented by the following linear equation.

a. 5 − x = 3 c. 5x + 3 = 3x + 9

b. x – 2 = 3x + 4 d. 8 – x = 2x – 1

4. Write a linear equation with one variable for

each of the following statements.




a. If Rp500.00 is added to Fia’s money, it will

become Rp 5,000.00.

b. After 7 books are taken by Ida, Ifa has 12

books left.

c. If Fitri’s money is multiplied by 2, it will

become Rp 15,000.00.

d. If Dani’s money is given to his two younger

brothers, each of them will have Rp 3,500.00.

e. After it is added Rp 50,000.00, Mother’s money

becomes Rp75,000.00.


buksis-4.2 revisi akhir

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