# Identifying a Solution to a Linear Equation by Substitution

In the following applet, you are given three possible solutions. Which one is correct? Figure it out by replacing the with one of the numbers given until you find one that fits.

# Evaluate a Quadratic Expression for some value x

A quadratic expression has and ‘unknown squared’ term, but not cubed or any higher exponent.

When we begin with an *expression*, we can’t solve it. There’s nothing to solve – there is no other side that puts a condition on the value of the unknown.

We can change its form by factoring, by grouping, by reordering, by gathering like terms etc. We can find out its value for certain values of unknowns. Those are the things we can do with expressions.

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