Iconic +covalent is the answer to this
Answer:
9 (1-2x²)
Explanation:
The given expression is:
30 - 9x²*2 - 21 - 4 + 4
The first step is to compute the multiplication. This will give:
30 - 18x² - 21 - 4 + 4
Then, we will add like terms as follows:
(30-21-4+4) - 18x²
= 9 - 18x²
Finally, we can take the 9 as a common factor from both terms, this will give:
9 (1-2x²)
Hope this helps :)

WHAT IS AN IONIC BOND


kossel explained that inert gases r inert due to the electronic configuration which contains 8 electrons in their outermost shell
And other elements loss and gain electrons to form ions and to have electronic configuration same as Noble gas and to get stable
#SARDAR JI.