Question

Please help if you can!
solve the system by substitution.
2x+y=-11
3x-4y=11
a.(3,5) b.(-5,-3) c. (-3,-5) d.(5,3)

Answer 1

well take the first equation, and get y alone. so to do that, you subtract 2x from both sides to get y=-2x-11

Answer 2

then sub that in in the second equation for y to get (3x)-4(-2x-11)=11

Answer 3

then you get 3x+8x+44=11

Answer 4

c. (-3,-5

Answer 5

then simplify to 11x=-33 so x=-3

Answer 6

Thank you @tfht for explaining it.

Answer 7

you have 2x+y = -11
compute for x or y using second equation
let say solving for x
3x-4y = 11
3x = 4y+11
x = (4y+11)/3
then substitute x in the 1st equation.
2((4y+11)/3)+y = 11
then solve for y.

Answer 8

then you sub -3 in for x to get 3(-3)-4y=11 then simplify it to -9-4y=11 then -4y=20 so y=-5. and yup no problem! i love math and so i come on here when im bored lol. glad i could help!

Answer 9

I don't understand it. but when people explain things to me it actually helps me understand it more. Math is not my strongest subject.

Answer 10

@tfht can you help me with another problem?

Answer 11

sure!

Answer 12

what is the solution of the following system.
-3x-2y=-12
9x+6y=-9
(2,1) b.no solutions c. (-2,-1) d. infinitely many solutions

Answer 13

no solution

Answer 14

ok so here i would simplify the second equation down to 3x+2y=-3

Answer 15

so then you could get x alone or y alone, im going to go for x and get 3x=-2y-3 then divide everything by 3 to get x=-2/3y-1 and sub that in for x in the first equation

Answer 16

you will see nooooo solution

Answer 17

-3(-2/3y-1)-2y=-12 which equals 2y-2y=-12 so that simplifies down to 0=-12 but that isnt possible, so it's no solution

Answer 18

Thank you to both of you! @tfht and @hazem-wardat

Answer 19

yup!

Answer 20

wlc