Question

Find the missing term: (x+3)² = x² + 6x + _____

Answer 1

It would be 9.

Explanation:

To do this, lets expand the equation (x+3)^2 by turning it into:

(x+3)(x+3)

Now, lets try something called the FOIL method. This is where all of the terms of the equation are multiplied in the order:

1) First

2) Outer

3) Inner

4) Last

So in (x+3)(x+3), each of the first parts of each parentheses box are x's, and x times itself equals x^2 so:

x^2 + ? + ? so far.

Next, with the Outer & Inner parts, they would be x * 3 and 3 * x. With this, you would get 3x and 3x. These can be added to get 6x, the middle part of the equation.

x^2 + 6x + ? so far.

Lastly, for the answer. Time to do the last part of each parentheses box, you would get 3 * 3, which gives you 9.

x^2 + 6x + 9.

Answer 2

9

Explanation:

The formula for (a + b)^2 expands out to: a^2 + 2ab + b^2. In the case of this problem, a equals x and b equals 3. We can substitute to get:

(a + b)^2 = a^2 + 2ab + b^2

(x + 3)^2 = x^2 + 2(x)(3) + (3)^2

(x + 3)^2 = x^2 + 6x + 9

So, the missing term is 9.

Another way to do this is to multiply (x + 3)(x + 3) since it's the same thing:

(x + 3)(x + 3)

x^2 + 3x + 3x +9

x^2 + 6x + 9

By solving this way, you get the same answer.