[191] Consider the quartic equation
The coefficient of the first term may be eliminated by dividing through by it, yielding
Rewrite this equation as
x4 + bx3 + cx2 + dx + e = 0
Let
Hence
Then
z4 + lz2 + mz + n = 0
where
Divide through by n to change constant coefficient to 1.
[192] Let
Then
Where
The last quartic may be factored
Note that
The last two formulas are plotted in the
accompanying chart, allowing b1 to be obtained in
terms of 
and
. Then
The quartic factors may be readily solved to
obtain the roots 
and 
. Then, working back through the preceding
derivation
andas given in preceding derivation.
