Let's do the long division
color(white)(aaaa)aaaa5x^4-3x^3+2x^2-15x4−3x3+2x2−1color(white)(aaaaaaaa)aaaaaaaa|∣x^2+4x2+4
color(white)(aaaa)aaaa5x^45x4color(white)(aa aaaa)aaaaaa+20x^2+20x2color(white)(aaaaaaaaaaa)aaaaaaaaaaa|∣5x^2-3x-185x2−3x−18
color(white)(aaaa)aaaa0-3x^30−3x3color(white)(aa a)aaa-18x^2−18x2color(white)(aaaaaaa)aaaaaaa
color(white)(aaaaaa)aaaaaa-3x^3−3x3color(white)(aaaa)aaaa-18x^2-12x-1−18x2−12x−1color(white)(aaaaaaa)aaaaaaa
color(white)(aaaaaaaa)aaaaaaaa00color(white)(aaaaa)aaaaa-18x^2-12x−18x2−12xcolor(white)(a)a-72−72
color(white)(aaaaaaaaaaaaaaaaa)aaaaaaaaaaaaaaaaa00color(white)(aaa)aaa+12x+12xcolor(white)(aa)aa+71+71
Therefore,
(5x^4-3x^3+2x^2-1)/(x^2+4)=5x^2-3x-18+(12x+71)/(x^2+4)5x4−3x3+2x2−1x2+4=5x2−3x−18+12x+71x2+4
The quotient is =5x^2-3x-18=5x2−3x−18
The remainder is =12x+71=12x+71