Which statement proves a triangle cannot have sides of 3 cm, 4 cm, and 9 cm I know it's not the first one.

3 + 4 > 9

Step-by-step explanation:

Now, when we have 3 sides of a triangle, the sum of the length of any two sides must be greater than the third side

Thus, we have that;

3 + 4 > 9

This is because the above is impossible

Others are quite possible mathematical expressions

step-by-step explanation:

let m = monomial

let t = trinomial

so, m times t = t.

monomial times a trinomial = another trinomial.