Question

x³ - 4x² - 17x + 60 = 0

Answer 1

\(x^3-4x^2-17x+6x=0\)

\(\Leftrightarrow\left(x^3+4x^2\right)-\left(8x^2+32x\right)+\left(15x+60\right)=0\)

\(\Leftrightarrow x^2\left(x+4\right)-8x\left(x+4\right)+15\left(x+4\right)=0\)

\(\Leftrightarrow\left(x+4\right)\left(x^2-8x+15\right)=0\)

\(\Leftrightarrow\left(x+4\right)\left(x-5\right)\left(x-3\right)=0\)

\(\Leftrightarrow\left[\begin{array}{nghiempt}x+4=0\\x-5=0\\x-3=0\end{array}\right.\)\(\Leftrightarrow\left[\begin{array}{nghiempt}x=-4\\x=3\\x=5\end{array}\right.\)

 

Answer 2

bấm máy tính ta có x1 = -4

x2 = 5

x3= 3