Question

solve 11x +15y +23 =0, 7x-2y-20 by elimination method

Answer 1

11x +15y +23=0
11x +15y = -23..........(I)

7x-2y-20=0
7x-2y=20..............(ii)

Multiply eqn.1 by 2 & eqn.2 by 15.Then

22x+30y=-46..........(iii)
105x-30y=300.......(iv)

Add eqn 4 & 3.Then,

105x-30y=300
22x+30y=-46
=127x=254
x=254/127
x=2.

Put the value of x in eqn 2 .then,
7×2-2y=20
14-2y=20
2y=20-14
2y=6
y=6/2
y=3.

Answer 2

11x + 15y + 23 = 0--------->i

=> 11x + 15y = 0

7x - 2y - 20 = 0

=> 7x - 2y= 20---------->ii

Multiplying equation i by 2 and equation ii by 15

Therefore, 22x+30y=-46

                 105x-30y=-300

                ----------------------

                 127x=-254

                 x=2

Substituting the value of x in equation ii

7*-2-2y=-20

-14-2y=-20

2y=-20+14

2y=-6

y==3