Answer:
The third option
Step-by-step explanation:
Given
(a + 3)(- 2a² + 15a + 6b²)
Each term in the second factor is multiplied by each term in the first factor, that is
a(- 2a² + 15a + 6b²) + 3(- 2a² + 15a + 6b²) ← distribute both parenthesis
= - 2a³ + 15a² + 6ab² - 6a² + 45a + 18b² ← collect like terms
= - 2a³ + 9a² + 45a + 6ab² + 18b² → C
Answer:
The third side must be smaller than 20 inches and greater than 4 inches

Step-by-step explanation:
Let a, b and c be the lengths of triangle's sides. Then

Use this rule in your case. So, if a=12 and b=8, then

Hence, you get

From these inequalities, you can state that

So, c must be smaller than 20 inches and greater than 4 inches.
Answer: D
Step-by-step explanation: It fills the requirements