a function from real numbers to real numbers defined by f(x)=x⁶-3x⁵+8x³+5. is function one one onto

Post makes no sense. Is there a question?

I'm guessing the OP is asking whether the function is "one-to-one" (i.e. injective), and/or "onto" (surjective). Navpreet: please clarify your question.