Question

Can someone help me out with this? I''m not understanding how to solve these.

2y-4x=20
y+4x=1

Answer 1

x = -1.5 and y = 7.

Explanation:

2y - 4x = 20

y + 4x = 1

We solve by elimination. (Note that -4x + 4x = 0 so if we add the 2 equations the terms in x disappear):

Adding:

3y + 0 = 21

y = 21 /3 = 7

Now, to find the value of x we substitute y = 7 into the first equation and solve for x:

2y - 4x = 20

2(7) - 4x = 20

-4x = 20 - 14 = 6

x = 6/-4

x = -1.5

To check if our answer is correct we substitute in the second equation:

y + 4x = 1

7 + 4(-1.5) = 7 - 6 = 1. Correct.

Answer 2

You can use substitution. Using the second equation, you move the variables to different sides and end up with y=1-4x then you substitute this into the first equation. You will get 2(1-4x)-4x=20 then you simplify. Distribute the 2 to get 2-8x-4x=20. Then combine like terms to get -12x=18. Divide each side by -12 and you get x=-18/12 or -3/2. Then you plug this number into either equation to find y. y+ 4(-3/2) =1 then distribute 4. y-6 =1. Then you get y=7. You can check your answer by plugging in both x and y and seeing if the equation remains true. 7+ (4•-3/2) =1 is true. So your answer is (-3/2, 7)