Question

How do solve the following linear system?: `2x+6y=5 , -x - y = 8`?

Answer 1

`x=-53/4` and `y=21/4`

Explanation:

We have two equations here

`2x+6y=5` **......................(1) and

`-x-y=8` **......................(2)

Observe that we have `2x` in first equation and `-x` in second equation. So if we double (2) and add to (1), `x` will be eliminated and we get

`2x+6y-2x-2y=5+16` or `4y=21` i.e. `y=21/4`

putting this value in (2), we get

`-x-21/4=8` or `-x=8+21/4=(32+21)/4=53/4`

and `x=-53/4`