Question

solve by substitution: 2x+y=0
x-3y=-7

solve by elimination: 3x+4y=1
5x-3y=21

Answer 1

for substitution solve for one variable i usually do y,
2x+y=0, subtract 2x over from both sides, y=-2x
now we take -2x and plug it in for every y
x-3(-2x)=-7 simplify to x+6x=-7
7x=-7 x=-1 and plug into the original y=-2x and y=2
that's substitution

Answer 2

i was able to solve for y for the first time, but i wasnt able to solve for x

Answer 3

when you solve for y you just put it into the second one for every you see, and solve for x, getting it in all x's makes it solvable

Answer 4

i got down to x=-7+3y

Answer 5

Let us solve the first system of equations by the method of substitution.

2x+y=0-----(1
x-3y=-7
i.e. x= 3y-7 ----(2
Now substituting x= 3y-7 in equation ---(1 we find

2(3y-7)+y=0
6y-14 +y=0
i.e. 7y-14 =0
i.e. 7y =14
i.e. y =14/7
i.e. y =2
Now substituting y =2 in any of the equation say ---(2
we find x= 3y-7 = 3*2-7= 6- 7 = -1
x=-1
Hence solution set is {-1, 2}
@chevyguy

Answer 6

you can do it that way to so now what you do is take that (-7-3y) and plug into the other for x, so you have 2(-7+3y) +y =0 does that part make sense?

Answer 7

solving for x made sense thank you both!

Answer 8

what about solving for elimination?

Answer 9

Next, let us solve the second system of equations by the method of elimination.

3x+4y=1 -----(1
5x-3y=21 -----(2

Let us multiply eq (1 by 3 and eq (2 by 4 and adding (1 & (2

9x+12y=3 -----(1
20x-12y=84 -----(2
_________________________
29 x +0 =87

i.e. 29 x =87

i.e. x =87/29
i.e. x =3

Now substitutingx =3 in any of the equation say ---(1
we find;
3*3+4y=1

i.e. 9+4y=1
i.e. 4y= 1-9
i.e. 4y= -8
i.e. y= -8/4
i.e. y= -2

hence solution set is {3, -2}

@chevyguy

Answer 10

@chevyguy Your problem has been solved.

Answer 11

@dpasingh thank you so much! exactly what i needed was for someone to explain to me and show me what you did thank you so much!!!!!!!!!!

Answer 12

@chevyguy Most welcome dear