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

1 Answer
May 18, 2017

Given: #(x^4-2x^3+2x^2-3x+3)/(x^2-3)#

Write the divisor with a 0 coefficient for missing term

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))color(white)((x^4-2x^3+2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#

To determine the first term in the quotient divide the first term in the dividend by the first term in the divisor #x^4/x^2=x^2# write #x^2# in the quotient:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2color(white)(2x^3+2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#

Multiply the term in the quotient by the divisor:

#x^2(x^2+0x-3) =x^4+0x^3-3x^2#

Make it negative:

#-x^4-0x^3+3x^2#

Write it below the dividend:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2color(white)(2x^3+2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#

Perform the addition and bring down the x term:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2color(white)(2x^3+2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#

To find the next term in the quotient, divide the first term in the sum by the first term of the divisor:

#(-2x^3)/x^2=-2x#

Write it as the next term of the quotient:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2xcolor(white)(2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#

Multiply the term in the quotient by the divisor:

#-2x(x^2+0x-3) =-2x^3+0x^2+6x#

Make it negative:

#2x^3+0x^2-6x#

Write it below the sum:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2xcolor(white)(2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#
#color(white)(...............................)ul(2x^3+0x^2-6x)#

Perform the additions and bring down the constant term:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2xcolor(white)(2x^2-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#
#color(white)(...............................)ul(2x^3+0x^2-6x)#
#color(white)(..........................................)5x^2-9x+3#

To find the next term in the quotient, divide the first term in the sum by the first term of the divisor:

#(5x^2)/x^2=5#

Write it as the next term of the quotient:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2x+5color(white)(-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#
#color(white)(...............................)ul(2x^3+0x^2-6x)#
#color(white)(..........................................)5x^2-9x+3#

Multiply the term in the quotient by the divisor:

#5(x^2+0x-3)=5x^2+0x-15#

Make it negative:

#-5x^2+0x+15#

Write it below the sum:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2x+5color(white)(-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#
#color(white)(...............................)ul(2x^3+0x^2-6x)#
#color(white)(..........................................)5x^2-9x+3#
#color(white)(.......................................)ul(-5x^2+0x+15)#

Perform the addition:

#color(white)( (x^2+0x-3)/color(black)(x^2+0x-3))(x^2-2x+5color(white)(-3x+3))/(| color(white)(x)x^4-2x^3+2x^2-3x+3)#
#color(white)(....................)ul(-x^4-0x^3+3x^2)#
#color(white)(..........................)-2x^3+5x^2-3x#
#color(white)(...............................)ul(2x^3+0x^2-6x)#
#color(white)(..........................................)5x^2-9x+3#
#color(white)(.......................................)ul(-5x^2+0x+15)#
#color(white)(...............................................)-9x+18#

Because #-9x+18# is of order 1 and the divisor is of order 2, we stop and declare #-9x+18# to be the remainder.