How do you find the roots of the polynomial −x3+5x2−11x+55=0?
1 Answer
Jan 12, 2017
Explanation:
This cubic factors by grouping:
0=−x3+5x2−11x+55
0=(−x3+5x2)+(−11x+55)
0=−x2(x−5)−11(x−5)
0=−(x2+11)(x−5)
0=−(x2−(√11i)2)(x−5)
0=−(x−√11i)(x+√11i)(x−5)
Hence:
x=5 orx=±√11i
