Maths - Functions Help (1 Viewer)

[freezeice04]

This is a maths question I'm having trouble ewith:

f(x) = x^3 when x is larger than or equal to 3
= 5 when x is between 0 and 3
= x^2 - x + 2 when x is smaller than or equal to 0

Evaluate:

f(-n^2)

It says that the answer is n^4 + n^2 +2 but I have no idea why and I need an explanation. Any help would be greatly appreciated!

 

[lychnobity]

This is a maths question I'm having trouble ewith:

f(x) = x^3 when x is larger than or equal to 3
= 5 when x is between 0 and 3
= x^2 - x + 2 when x is smaller than or equal to 0

Evaluate:

f(-n^2)

It says that the answer is n^4 + n^2 +2 but I have no idea why and I need an explanation. Any help would be greatly appreciated!

Firstly, n² is always more than or equal to zero; therefore -n² is always less then or equal to zero

f(-n²) = (-n²)² - (-n²) + 2 = n^4 + n^2 +2

 

[hscishard]

Firstly, n² is always more than or equal to zero; therefore -n² is always less then or equal to zero

f(-n²) = (-n²)² - (-n²) + 2 = n^4 + n^2 +2

What he said.

 

[freezeice04]

I didn't realize that O.O For some stupid reason I thought -n^2 = great than 0 since a negative x a negative gives a positive but I guess it meant something else.

Thanks anyways.

 

[hscishard]

I didn't realize that O.O For some stupid reason I thought -n^2 = great than 0 since a negative x a negative gives a positive but I guess it meant something else.

Thanks anyways.

It would be correct if it was (-n)^2 as it will always be positive.

But -n^2 is -1 x n^2, so always positive times -1 will always give a negative.