These are the steps involved..When you encounter this type of qn where an equation has one root,substitute first and do the necessary to make your equation look similar like the one the qn wants..Remember to use what you have with you from the original equation for removal of the odd term..Isn't it the same if you are given two roots and then to form a new equation with new roots..You still have to use the values you already know in the first equation,right?..This qn does not negates the concept you learn before..Hope it helps. :)