F.2 maths

1. 7x+2y=0
x-6=0 x=6
7x6+2y=0
2y=-42
y=-21
2. 3x(1) 15x+9y+18=0-------(3)
5x(2) 15x-10y-115=0---------(4)
(3)-(4)
19y+133=0
y=-7
15x+9(-7)+18=0
15x=45
x=3

1. 7x + 2y = x - 6 = 0

Sol: 7x + 2y = 0 -------- (1)
x - 6 = 0 -------- (2)

From (2), x = 6 -----------(3)
Sub (3) into (1)

7(6) + 2y = 0
2y = -42
y = -21
The solution is x=6 and y=-21

The above equation is solved by the "method of substitution" !!



2. 5x + 3y +6 = 0
3x - 2y - 23 = 0

Sol: 5x + 3y = -6 -------(1)
3x - 2y = 23 -------(2)

(1) x 2, 10x + 6y = -12 --------(3)
(2) x 3, 9x - 6y = 69 ----------(4)

(3)+ (4), 19x = 57
x = 3

Put x = 3 into (3)

10(3) + 6y = -12
6y = -42
y = -7

Therefore, the solution is x = 3 and y = -7

The above equation is solved by the "method of elimination" !!