Δ(x)=∣∣
∣
∣∣2x3−3x25x+724x3−7x3x+217x3−8x2x−13∣∣
∣
∣∣=a0+a1x+a2x2+ a3x3+a4x4
R3→R3–3R2,R1→R1–2R2
=∣∣
∣
∣∣−6x3−3x2+14x3−x04x3−7x3x+21−5x3−8x2+21x−8x−70∣∣
∣
∣∣
=–1[(6x3+3x2–14x)(8x+7)–(5x3+8x2–21x)(x–3)]
By comparing the coefficient method
a0=0,a1=161,a3=–73,a4=–43,a2=46