I need help with y =2^3-4. To prove it it 1-to 1, onto or both.
I think I understand how to to prove that the function is one to one.
2^3-4=2^3-4 then +4 and then divide by 2, so we have x(1)^3=x(2)^3. They are even, if and only if x(1)= x(2) are the same. Therefore this is One to One function.
What about Onto function y =2^3-4.
Do I prove it by counterexample? Or otherwise? I can see that it's onto ....but how to write a proof.
Please someone help me! Thank you.