class 9th icse chapter 6
Answers
Question 1
Solve the pairs of linear (simultaneous) equations by the method of elimination by substitution:
8x + 5y = 9
3x + 2y = 4
Solution 1
8x + 5y = 9...(1)
3x + 2y = 4...(2)
(2)y =
Putting this value of y in (2)
3x + 2
15x + 18 - 16x = 20
x = -2
From (1) y = =
y = 5
Question 2
Solve the pairs of linear (simultaneous) equations by the method of elimination by substitution:
2x - 3y = 7
5x + y= 9
Solution 2
2x - 3y = 7...(1)
5x + y = 9...(2)
(2)y = 9 - 5x
Putting this value of y in (1)
2x - 3 (9 - 5x) = 7
2x - 27 + 15x = 7
17x = 34
x = 2
From (2)
y = 9 - 5(2)
y = -1
Question 3
Solve the pairs of linear (simultaneous) equations by the method of elimination by substitution:
2x + 3y = 8
2x = 2 + 3y
Solution 3
2x + 3y = 8...(1)
2x = 2 + 3y...(2)
(2) 2x = 2 + 3y
Putting this value of 2x in (1)
2 + 3y + 3y = 8
6y = 6
y = 1
From (2) 2x = 2 + 3 (1)
x =
x = 2.5