Question

If a+b=5 and a-b=3 then b=?

a) -2
b) 1
c) 2
d) 4
e) 8
i think the answer is 1?

Answer 1

a+b=5 and a-b=3 should be re-written as

a+b=5

a-b=3

Combine these to obtain 2a = 8. Then a =4. Sub 4 for a in either equation. If you do that in the 2nd equation you'll get 4 - b = 3, or b = 1.

Then the solution is (4,1). Please note that this has 2 parts: 4 and 1.

These are the coordinates of the solution, the point at which the 2 lines intersect.

Answer 2

Lets use elimination to solve the system of equations. We do this by adding the two equations terms together.

a + b = 5

a - b = 3

(a + a) + (b + (- b)) = (3 + 5)

2a + 0 = 8

We can then solve this new equation for a.

2a = 8

a = 4

After this, we can plug in the value of a into one of the equations and solve for b.

a + b = 5

4 + b = 5

b = 1

You're correct, the answer is 1.