A little help would be nice

13). -2x³ + x² + 1   14). x + 10y - 10z   15). -2x³ + x² + 1

Step-by-step explanation:

13). (x³ - x² + 4) - (3x³ - 2x² + 3)

= x³ - x² + 4 - 3x³ + 2x² - 3

= x³ - 3x³ - x² + 2x² - 3 + 4

= -2x³ + x² + 1

14). (3x + 4y - 3z) - (2x - 6y + 7z)

= 3x + 4y - 3z - 2x + 6y - 7z

= 3x - 2x + 4y + 6y - 3x - 7z

= x + 10y - 10z

15). (x³ - x² + 4) - (3x³ - 2x² + 3)

= x³ - x² + 4 - 3x³ + 2x² - 3

= x³ - 3x³ - x² + 2x² + 4 - 3

= -2x³ + x² + 1

false

step-by-step explanation:

the reason i say this is because for a certain length of sides you can pick any two and the length is wither equal or greater than the third side and in this case it's not.

3 + 5 = 8

8 is smaller than 9 which is the third side.

hope this : )