Question

X+2y=5 and 4x-12y=-20 solve using elimination and substitution

Answer 1

Answer:

(1,2)

Step-by-step explanation:

Substitution:

x + 2y = 5  Solve for x

x = -2y + 5  Substitute -2y + 5 in for x in the second equation

4x - 12y = -20

4(-2y + 5) - 12y = -20  Distribute the 4

-8y + 20 - 12 y = -20  Combine the y term

-20y + 20 = -20  Subtract 20 from both sides

-20y = -40  Divide both sides by -20

y = 2

Plug y into either of the 2 original equations to get x.

x + 2y = 5

x + 2(2) = 5

x + 4 = 5

x = 1

The answer is (2,1).

Elimination:

x + 2y = 5      4x - 12y = -20.  We want to eliminate with the x or the y.  I am going to eliminate the x's that means that I have to multiply the first equation all the way through by -4

(-4)(x + 2y) = (5) (-4)  That makes the equivalent expression

-4x - 8y = -20  I will add that to 4x - 12y = -20

4x - 12y = -20

0x -20y = -40

-20y = -40

y = 2.  Plug 2 into either the 2 original equation to find x.  This time I will select the second original equation to find x.

4x -12y = -20

4x - 12(2) = -20

4x - 24 = -20

4x = 4

x = 1