Question

Which ordered pair in the form (a,b) is a solution of this equation?

7a - 5b = 28

1. 0,4
2. 4,0
3. -3,-2
4. -2,-3

Answer 1

You can figure out the answer to this by plugging in each set of coordinates into the equation and solving.

7a - 5b = 28 Plug in the coordinates

1. 7(0) - 5(4) = 28 Multiply
0 - 20 = 28 Subtract
-20 ≠ 28

2. 7(4) - 5(0) = 28 Multiply
28 - 0 = 28 Subtract
28 = 28

3. 7(-3) - 5(-2) = 28 Multipy
-21 - -10 = 28 Simplify the double negative
-21 + 10 = 28 Add
-11 ≠ 28

4. 7(-2) - 5(-3) = 28 Multiply
-14 - -15 = 28 Simplify the double negative
-14 + 15 = 28 Add
1 ≠ 28

As you can see, the only set of coordinates that worked was 2. (4, 0).