For the given function, find out the largest open interval of the domain over which the function is decreasing. 

If the function $h\left(x\right)=-2x^2$ is graphed, how does its graph compare to the graph of $y=2x^2$?

If the function $g\left(x\right)=6\sqrt{-x}$ is graphed, how does its graph compare to the graph of $y=6\sqrt{x}$?

For the following polynomial expression, perform the indicated operations to simplify.

(9k² - 7x)(9k² + 7x)

Rewrite the following expression by factoring it completely:

15a³b⁴ + 20a²b² + 40ab³

Evaluate:

11 - 4 • 9 - (-3)⁴

Perform the indicated operations on the following complex numbers and have the answer in standard form.

$\frac{5}{2-3i}$

Simplify the following expression and express the answer in standard form.

$\sqrt{-121}$