algebra 2 help?

Question

solve by substitution
3x - 2y = -80
2x - y = -57

A (26, 19)
B (11, -37)
C (8, 17)
D (14, -34)
E (12, 28)
F (-34, -11)

Answer 1

Solve the second equation for y:

2x - y = -57
y = 2x + 57

... then replace "y" with "2x +57" in the first one.

3x - 2y = -80
3x - 2(2x+57) = -80
3x - 4x - 114 = -80
-x = 34
x = -34

Already that narrows down to (F), the only answer with x=-34, however let's finish the problem:

Go back to either equation and substitute x=-34 to get y:

2x - y = -57
2*(-34) - y = -57
-68 - y = 57
-y = 11
y = -11

And then try the other equation with the values you've calculated (-34,-11) and see if it is correct:

3x - 2y =? -80
3*(-34) - 2*(-11) =? -80
-102 + 22 =? -80
-80 = -80

Answer 2

Take the second equation,
2x-y=-57
solve it in respect of y, mark it as equation 1
-y=-57-2x,
y=57+2x .....1
Take the first equation,
3x-2y =-80
and subtitute y with equation 1
3x - 2(57+2x)=-80
then solve it for x, and mark it as equation 2
3x - 114 -4x = -80
-x-114=-80
x+114=80
x=80-114=-34 ... 2
then subtitute equation 2 to equation 1
y=57+2x
y=57+2(-34)
y=57-68=-11

So (x=-34 and y=-11)
The answer is F.

Tips : you dont have to use any special method to answer this question though, you just have to try each answer, and choose the one that fit.

Answer 3

1. 3x-2y=-80
2. 2x-y=-57
Solve one of the equations for y.
2. 2x-y=-57
2x+57=y
Substitute this in as y in the other equation, and solve.
1. 3x-2y=-80
3x-2(2x+57)=-80
3x-4x-114=-80
-x=34
x=-34
Once you have x, put it back in one of the equations to find y.
2. 2x-y=-57
2(-34)-y=-57
-68-y=-57
-11=y
So the answer is F, (-34, -11).

Answer 4

3x - 2y = -80
2x - y = -57 add y+57 to each side
y=2x+57
3x - 2y = -80 substitute 2x+57 for y
3x-2(2x+57)=-80 distribute -2
3x-4x-114--80 add 114 to each side
-x=34 divide both sides by -1
x=-34
y=2x+57 substitute -34 for x
y=-68+57
y=-11
(-34, -11)

F (-34, -11) is correct

Answer 5

3x - 2y = -80
2x - y = -57

1º
2x - y = -57
-v = -57 - 2x
-1*v = -57 - 2x
v = (-57 - 2x)/-1
v = -(57 + 2x)/-1
v = (-1*(57 + 2x))/-1
v = 57 + 2x

2º
3x - 2y = -80
v = 57 + 2x

3x - 2y = -80
3x - 2(57 + 2x) = -80
3x - 114 - 4x = -80
-x - 114 = -80
-x = 34
x = 34/-1
x = -34

3º
v = 57 + 2x
x = -34

v = 57 + 2x
v = 57 + 2(-34)
v = 57 - 68
y = -11

x = -34, y = -11

F (-34, -11)

Answer 6

7x + y = 18 -------- equation i

11x + 3y = - 6 ----- equation ii


Multiply by '11' in equation i and by '7' in equation ii

(7x)(11) + (y)(11) = (18)(11) -------- equation i

(11x)(7) + (3y)(7) = (- 6)(7) ----------- equation ii


77x + 11y = 198 ---------- equation i

77x + 21y = - 42 ----------- equation ii

and subtract the both equations

+ 77x + 11y = + 198 ---equation ii

+ 77x + 21y = - 42 ----------- equation ii
- - +
----------------------------------
-10y = 240 ----------- equation iii

Divide 240 by 10 in equation iii

y = 240/-10

y = -24

Substitute the value of y = - 24 in equation i

7x + y = 18 -------- equation i

7x + (-24) = 18

7x - 24 = 18

7x = 18 + 24

7x = 42

x = 42 / 7

x = 6

x = 6 and y = - 24

The answer is D (6, -24)


NOTE: + + = +

+ - = -

- - = +

Answer 7

ur answer is F u have to solve for x than subsitute n solve for y