Question

Find two numbers a and b whose sum a+b is -3 and whose difference a-b is -7

Answer 1

a = -5

b = 2

Explanation:

a + b = -3

a - b = -7 Add together

2a = -10 Divide both sides by 2

a = -5

Use either of the two original equations to find b.

a + b = -3 Substitute -5 for a

-5 + b = -3 Add 5 to both sides

-5 + 5 +b = -3 + 5

b = 2

Check:

a + b = -3

-5 + 2 = -3

-3 = -3 Checks

a - b = -7

-5 - 2 = -7

-7 = -7 Checks