How do you long divide #(x^2+4x-39)/(x+8)#?

1 Answer
David B. · P dilip_k
Mar 12, 2016

#(x^2+4x-39)/(x+8)=x-4-7/(x+8)#

Explanation:

Performing polynomial long division is much like regular long division. We write the polynomial and its divisor down in long division form and go through the normal steps of long division. Then we guess our first term in the quotient, which should subtract from the first term in the dividend shown in #color(red)("red")# below:

#{:("",{:("",color(red)(x),color(blue)(-4)):}),(x+8,bar(")"{:(x^2,+4x,-39):})),(,{:(color(red)(-x^2 -8x),):}),(,{:(bar(" "-4x),-39,):}),(,{:(" ",color(blue)(4x),color(blue)(+32),):}),(,{:(" ",bar(" "-7)):}):} #

We then repeat this step for the next power of #x# shown in #color(blue)("blue")#. We end up with a remainder of #-7# which we treat in the normal way by dividing it by the divisor and adding it to the quotient:

#(x^2+4x-39)/(2x+5)=x-4-7/(x+8)#

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