Give all zeros of P(x)=x3+9x. I solved and got 0,3,-3 but I'm told these are incorrect zeros.

Answer 1

P(x) = x³ + 9x = x(x² + 9) = 0; x = 0 or x² + 9 = 0; x = ±3i

Answer: 0, ±3i

Answer 2

Hi LPL,

I see, you probably got mixed up between the solution of this equation and the equation x3 - 9x. the solution you gave is for the latter.

Answer 3

x^3 + 9x

= x(x^2 +9)

set each factor = 0 and solve for x

x= 0 is one zero

x^2+9 =0

x^2=-9

x = square root of -9

x = + or - 3i

zeroes are -3i, 3i and 0

("0's" is spelled zeros in the US, but zeroes in Britain, roughly, but the US can go either way)

Your answer was right, if you just added an i to the 3 and -3. Very close. where the real and imaginary cross or get close. where myth and reality merge or diverge.