How do you divide (x^4+3x^3-12x-6 ) / ( x^3+2x^2-4 )?

1 Answer
Mar 30, 2016

x+1 -(2x^2+8x+2x)/(x^3+2x-4)

Explanation:

Only divide using the most significant figures ie ?-:color(green)(x^3)

" "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)

'~~~~~~~~~~~~~~~~~~~~~~~~~

color(blue)("Step 1 ")x^4/x^3=color(magenta)(x)

" "color(magenta)(x)
Write as: " "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Step 2 ")

color(green)(x^3+2x^2-4)
underline(" "color(magenta)(x))" "->"Multiply"
""color(blue)(x^4+2x^3-4x)

Write as:
" "x
" "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)
" "underline(color(blue)(x^4+2x^3-4x))" "->" Subtract
" "0+color(red)(x^3)-8x-6" bring down the 6"
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

color(blue)("Step 3 ")

(color(red)(x^3))/(color(green)(x^3)) =color(magenta)(+1)

Write as:
" "x color(magenta)(+1)
" "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)
" "underline(x^4+2x^3-4x)" "->" Subtract
" "0+color(red)(x^3)-8x-6

color(green)(x^3+2x^2-4)
underline(" "color(magenta)(+1))" "->"Multiply"
""color(blue)(x^3+2x^2-4)
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

color(blue)("Step 4 ")

Write as:
" "x +1
" "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)
" "underline(x^4+2x^3-4x)" "->" Subtract
" "0+x^3"-8x-6
" "underline(color(blue)(x^3+2x^2-4))" "-> Subtract
These do not line up any more as we have an extra term. For convenience change the order. This can be sorted out later.
Write as:
" "x +1
" "color(green)(x^3+2x^2-4)" |"bar(x^4+3x^3-12x-6)
" "underline(x^4+2x^3-4x)" "->" Subtract
" "0+x^3"-8x-6
" "underline(color(blue)(x^3+0color(white)(.)-4+2x^2))" "-> Subtract
" "0color(white)(.)-8x-2-2x^2 >>>>

The remainder is:" "-2x^2-8x-2 We can not divide any further as its most significant value is less than the x^3 in x^3+2x^2-4

So we express it as (-2x^2-8x-2)/(x^3+2x^2-4) = -(2x^2+8x+2)/(x^3+2x-4)
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

=>(x^4+3x^3-12x-6)/(x^3+2x-4)" " =" " x+1 -(2x^2+8x+2)/(x^3+2x-4)