Question

If 4x + 2y = 14 and x - 2y = 6, what is the value of y?

Answer 1

y must be -1

Explanation:

We are given the system of linear equations

4x + 2y = 14

x - 2y = 6

and need to find the value of y. Combining the two equations yields

5x = 20, and so we know that x must be 4.

If x is 4, then the second equation becomes 4 - 2y = 6, or -2y = 2.

Then y must be -1.

Answer 2

y is -1

Explanation:

`4x + 2y = 14 - - - (a) \\ x - 2y = 6 - - - (b)`

(a) + (b):

`5x = 20 \\ x = 4`

therefore:

`x - 2y = 6 \\ 4 - 2y = 6 \\ 2y = - 2 \\ y = - 1`