Question

How do you solve `x-5y=4` and `4x+8y=-5` using substitution?

Answer 1

`x = 1/4 , y = -3/4`

Explanation:

Begin by labelling the equations- easier to follow.

x - 5y = 4 ................................(A)

4x + 8y = -5 ..............................(B)

Rearrange (A) to obtain : x = 4 + 5y ...................(C)

Now substitute this for x in (B)
4(4 + 5y ) + 8y = -5 → 16 + 20y+8y = -5 → `y = -21/28 = -3/4`
now substitute `y = -3/4 " in " (C)`
`x = 4 + 5xx(-3/4) = 1/4`
Check by substituting values of x and y in (A) and (B)