Divide using long division
x4 - 8x3 + 2x2 + 24x + 9 by x2 - 2x - 1
Start with this:
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x² goes into x4 x² times, so write that
above over the x² term
x²
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
Now multiply the x² by each of the terms at the far left,
and write the three terms that you get under the first three
terms, and draw a line under them:
x²
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
Now we subtract vertically by mentally changing
the sign of the bottom number and adding:
x²
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x²
Bring down the next term:
x²
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
Now x² goes into -6x³ -6x times, so we write
-6x³ ar the top:
x² - 6x
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
Now multiply the -6x by each of the terms at the far left,
and write the three terms that you get under the three
terms at the bottom, and draw a line under them:
x² - 6x
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
-6x² + 12x² + 6x
-----------------
-9x² + 18x
Bring down the last term:
x² - 6x - 9
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
-6x² + 12x² + 6x
-----------------
-9x² + 18x + 9
x² goes into -9x² -9 times, so write -9 on the
end at the top:
x² - 6x - 9
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
-6x² + 12x² + 6x
-----------------
-9x² + 18x + 9
Multiply the -9 be each term at the left as
write them at the bottom:
x² - 6x - 9
--------------------------
x² - 2x - 1)x4 - 8x³ + 2x² + 24x + 9
x4 - 2x³ - x²
--------------
-6x³ + 3x² + 24x
-6x² + 12x² + 6x
-----------------
-9x² + 18x + 9
-9x² + 18x + 9
--------------
Then when you subtract you get 0 remainder,
so the answer is
x² - 6x - 9
Edwin