Question

Select the choice below that could be the first step in solving the following system of equations using substitution:
2x − 4y = 18
3x − y + 10 = 0
Multiply the second equation by -4
Write the second equation in terms of y
Multiply the first equation by 2
Replace the right side of the first equation with the second equation

Answer 1

Write the second equation in terms of y. If you do that, it's then y = something, and you can SUBSTITUTE that in the first equation (that's why it's called substitution)

Answer 2

Solve using substitution:
-y − 5x = -7
2y − 2x = 14
Infinitely many solutions
No solution
(7/5, 14)
(0, 7)

Answer 3

Okay, multiply the first equation by 2

so now you have

-2y -10x = -14
2y -2x = 14

(add together, y's and 14's cancel out)

-12x = 0
x = 0

sub back in to get y

2y - 0 = 14
2y = 14
y =7

therefore, the solution is (0, 7)

Answer 4

Solve using substitution:
-2x − y + 1 = 0
2x = -13 − 3y
(1, -9)
(3, -5)
(-2, 5)
(4, -7)

WHAT ABOUT THIS ONE

Answer 5

okay, for this one, just move -y over to the other side in the first equation

so now you have y = 1 - 2x

sub that into the second equation

2x = -13 -3y
2x = -13 - 3(1-2x)
2x = -13 -3 +6x
2x = -16 + 6x
-4x = -16
x = 4

and then find y...

y = 1 - 2x
y = 1 - 2(4)
y = 1 - 8
y = -7

so your final answer is (4, -7)