Question

Which equation is an identity?

Answer 1

Answer:

Equation 3

Step-by-step explanation:

An identity is, simply put, an equation that is always true. 1 = 1, 2 = 2, and x = x are all examples of identities, as there's no case in which 1 ≠ 1, 2 ≠ 2, and x ≠ x. Essentially, if we can manipulate and equation so that we end up with the same value on either side, we've found an identity. Let's run through and try to solve each of these equations to see which one fulfills that condition:

8 - (6v + 7) = -6v - 1

8 - 6v - 7 = -6v - 1

1 - 6v = -6v - 1

1 = -1

This is clearly untrue. Moving on to the next equation:

5y + 5 = 5y - 6

5 = -6

Untrue again. Solving the third:

3w + 8 - w = 4w - 2(w - 4)

2w + 8 = 4w - 2w + 8

2w + 8 = 2w + 8

If we created a new variable z = 2w + 8, we could rewrite this equation as

z = z, which is always true. We can stop here, as we've now found that equation 3 is an identity.