# Evaluating a variable expression 2

#### rodgerst414

##### New member
Evaluate the variable expression when a=3,b=1 and c=-2

b^2-4ac. This is new to me so please explain how to do this.

#### MarkFL

Staff member
Okay, what you want to do is let the 3 variables take on the given values, and put these into the expression you are asked to evaluate:

This would give us:

$(1)^2-4(3)(-2)$

Now, can you compute this expression following the rules of arithmetic?

#### MarkFL

Staff member
For future topics, I highly recommend using a title that briefly describes the problem. For example, a good title for this topic is "Evaluating a variable expression". This lets our helpers know exactly what kind of problem is being discussed.

#### rodgerst414

##### New member
For future topics, I highly recommend using a title that briefly describes the problem. For example, a good title for this topic is "Evaluating a variable expression". This lets our helpers know exactly what kind of problem is being discussed.