The polynomial equation x cubed + x squared = negative 9 x minus 9 has complex roots plus-or-minus 3 i. What is the other root? Use a graphing calculator and a system of equations.
–9
–1
0
1
2 answers
so, have you used your calculator?
x cubed + x squared = negative 9 x minus 9
why not ....
x^3 + x^2 = 9x - 9
x^3 + x^2 - 9x + 9 = 0
you know x^2 + 9 is a factor, so
by either long division or synthetic division .....
x^3 + x^2 - 9x + 9 = 0
--> (x^2+9)(x+1) = 0
so the other root is -1
why not ....
x^3 + x^2 = 9x - 9
x^3 + x^2 - 9x + 9 = 0
you know x^2 + 9 is a factor, so
by either long division or synthetic division .....
x^3 + x^2 - 9x + 9 = 0
--> (x^2+9)(x+1) = 0
so the other root is -1
1 answer