Question

solve the system by substitution please help
{2x+y=-11
{3x-4y=11
A. (3,5)
B. (-5,-3)
C. (-3,-5)
D. (5,3)

Answer 1

2x+y=-11------->y= -2x-11-----(1
{3x-4y=11-------(2
from 1 and 2
3x-4(-2x-11)=11
i.e. 3x+8x+44=11
i.e. 11x=11-44
i.e. 11x=-33
i.e. x=-33/11
i.e. x=-3

from eq 2

y= -2x-11 = -2(-3) -11=6-11= -5
Thus {x,y}={-3,-5} which is the required ans

Answer 2

2x+y=-11---(1)
3x-4y=11---(2)

in equation (1)

2x+y=-11
2x=-11-y
x=-11-y/2

put in equation (2)

3(-11-y/2)-4y=11
-33-3y/2-4y=11
-33-3y-8y=22
-33-11y=22
-11y=22+33
-11y=55
y=-55/11
y=-5

put in equation (1)

2x-5=-11
2x=-11+5
2x=-6
x=-6/2
x=-3

(x,y)=(-3,-5)