The easiest method for expanding these brackets is to use the FOIL method of expansion.
This ensures you multiply every aspect of the brackets together.
First - take the first terms of the brackets (so, x and x) and multiply them together: for this example that gives x2.
Outside - take the two outermost terms of the brackets (x and 5) and multiply them together: for this example that gives 5x.
Inside - take the two innermost terms of the brackets (3 and x) and multiply them together: for this example that gives 3x.
Last - take the last terms of the brackets (so 3 and 5) and multiply them together: for this example that gives 15.
Some people may draw lines between terms when doing this (as seen in the diagram above) leaving you with a “crab claw” around the brackets.
Write down everything you have worked out as one long expression:
x2 + 5x + 3x + 15
Then, we will simplify this expression by grouping any “like” terms (this just means adding together any bits with x where they have the same power).
This leaves us with our final answer, which is:
x2 + 8x + 15