Identities

Answer : A

Here is the skill.
We can substitute x = 2 to eliminate b. Then, we get 7 + 2a = -3. Therefore, we get a = -5.
By substitute back a = -5, we can get b = -3.

Concept about identities

An equation is an identity if any values of x satisfy the equation.
E.g. x² – 1 = (x + 1)(x – 1)