Page 104 - Mathematics_F1

Substitute equation (3) into equation 0.2x +  0.5y = 2
(2) to obtain,  1.4
 − 0.4x + 0.3y = −
7   3– 5y   + 8y = 10 Solution
 6  Transform the equations into
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Simplification gives, equations with integer coefficients. Tanzania Institute of Education
21 35y− Multiply by 10 both sides of the
+ 8y = 10
6 equations.
Further simplification gives,  10(0.2x + 0.5 ) 2 10y = ×
 21– 35y   10( 0.4x + 0.3 )y = − 1.4 10
×
−
6 10 6
 + 8y ×= × 

 6  (1)
(i)
21 35y− + 48y = 60  − 2x +  4x + 5y = 3y = 20 − 14 (ii)
13y = 60 21−  (2)
13y = 39 Use equation (1) to make y the
39 subject. That is,
y = 13 5y = 20 2x−

= 3 2
Hence, y = 3. y = 4 − x (iii) (3)
5
3
Substitute y = into equation (3) to Substitute equation (3) into (2).
obtain the value of x. That is, Thus,
−
3 5(3)
x =  2 
6 − 4x + 3 4−  x =  − 14
3 15  5 
−
x = 6 4x− + 12 − 6 x = − 14
12 5
x = − Further simplification gives,
6 26

= − 2 − 5 x = − 26
Therefore, x = − 2 and y = 3.
1 x = 1
5
Example 5.36 x = 5

5
Find the solution of the following Substitute x = in equation (3) to Mathematics Form One
simultaneous equations by obtain the value of y. That is,
substitution method. 2 x
y = 4 − 5

97

25/09/2025 15:01:15
Mathematics form 1.indd 97 25/09/2025 15:01:15
Mathematics form 1.indd 97