Question

Consider the following pair of equations:

y = −2x + 8
y = x − 1

Explain how you will solve the pair of equations by substitution. Show all the steps and write the solution in (x, y) form.

Answer 1

y+2x=8.....(1)

y-x=-1.......(2)

in equation (2) make x the subject of the formula x=y+1

substitute y+1 for x in equation (1)

y+2(y+1)=8

y+2y+2=8

3y=8-2

y=2

substitute 2 for y in equation 2

y-x=-1

2-x=-1

x=2+1

x=3

y=2 x=3

Answer 2

y = -2x + 8 , y = x - 1 . they both equal y so you can plug them in to equal eachother . so now you have x - 1 = -2x + 8. get x on one side by itself. so change the - on the -2 and add. now you have 3x - 1 = 8 . add 1 to both sides to get rid of it. now you have 3x = 9 . divide both sides by 3. and x = 3 . now plug x into either equation . (the second is easier) so y = 3 - 1 . so y = 2 . (3,2)