How do you divide (x^3-3x-2) / (x+8) x33x2x+8 using polynomial long division?

1 Answer
May 20, 2016

(x^3-3x-2)/(x+8)" " =" " x^2-8x+61 -490/(x+8)x33x2x+8 = x28x+61490x+8

Explanation:

Using different variables but the approach is the same; have a look at:" " https://socratic.org/s/auC4VyMH

Solution without as much explanation as shown on the hyperlinked page.

#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

" "x^2-8x+61 x28x+61
x+8" "bar("| "x^3+0x^2-3x-2)x+8 ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯| x3+0x23x2
" "color(blue)(underline(x^3+8x^2 )" " larrx^2(x+8) " subtract")
" "color(brown)(0-8x^2-3x-2" " larr "Remainder")
" "color(blue)(underline(-8x^2-64x )" "larr -8x(x+8)" subtract")
" "color(brown)(0+61x-2" "larr" Remainder")
" "color(blue)(underline(61x+488)" "larr" "61(x+8)" subtract")
" "color(brown)(0-490" "larr" Remainder")

color(brown)("remainder "->-490/(x+8))

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Putting it all together")

color(blue)((x^3-3x-2)/(x+8)" " =" " x^2-8x+61 -490/(x+8)).....(1)

'@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
'@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
color(magenta)("Check")
x^2-8x+61-490/(x+8)

underline(" "x+8)" "larr" multiply"
x^3-8x+61x+0-(490x)/(x+8)" "larr" multiplied by "x

underline(" "+8x^2-64x+488+0-3920/(x+8))" "larr" multiplied by 8"
color(green)(x^3+0x^2-3x+488-(490x)/(x+8)-3920/(x+8))...(2)

'........................................

Consider -(490x)/(x+8)-3920/(x+8)

(-490(x-8))/(x-8)=-490
'...............................................
So equation (2) becomes

color(green)(x^3+0x^2-3x+488-490

color(green)(x^3-3x-2)

color(red)("Solution is correct")