INTRODUCING A USEFUL DODGE
75
We get
and .
(see example 5, p. 69); and
.
So that
Replace now first , then by its value.
Exercises VII
You can now successfully try the following. (See page 257 for Answers.)
(1) If ; ; and , find .
(2) If ; ; and , find .
(3) If ; ; and , find .