### Video Transcript

If π equals five plus two π and
π equals nine minus π, find the real part of π minus π .

Here we have two complex numbers to
find as five plus two π and nine minus π. We can see that the real part of π
is five and the real part of π is nine. The imaginary part of π is two and
the imaginary part of π is negative one. Weβre being asked to find the real
part of the difference between π and π . And we could absolutely work out
the entire answer to π minus π by collecting like terms. Thatβs five plus two π minus nine
minus π.

Itβs important that we use these
parentheses here because it reminds us that weβre subtracting everything inside
these brackets, nine minus π. If we distribute these parentheses,
we get five plus two π minus nine plus π, since subtracting a negative is the same
as adding a positive. Then we would simplify by
collecting like terms. However, thatβs probably a little
more work than we really need to do.

In fact, we recall that, to
subtract complex numbers, we simply subtract the real parts and then subtract the
imaginary parts separately. Weβre being asked to work out the
real parts of the complex number π minus π . So actually, we just need to
subtract the real part of π from the real part of π. We can formalise this and say that
the real part of π minus π equals the real part of π minus the real part of
π . We already saw that the real part
of π is five and the real part of π is nine. Five minus nine is negative
four. So the real part of π minus π in
this case is negative four.