# Introduction

You can only add terms when the variables are the same:

$4ab+6ab=10ab$
$4ab+6ad=4ab+6ad$

The same rule goes for powers:

$9x^2+2x^2=11x^2$
$9x^2+2x=9x^2+2x$

$5i^2+6j^2.k+8i^2+3j^2.k$
$=(5i^2+3i^2)+(6j^2.k+3j^2.k)$
$=8i^2+9j^2.k$