(x - 9)(x + 9) would give you x^2 - 81 when you get a plus and minus like that after you factor the middle term is canceled out so the answer would be (x - 9)^2
Answer:

Step-by-step explanation:
To solve an equation for one of its variables do that:
- Underline the variable
- Separate it one side and the other terms on the other side
- Make its coefficient equal to 1
Let us use these steps to solve our question
∵ V = πr²h
→ Underline r²
∴ V = π<u>r²</u>h
→ Take π and h to the other side by dividing both sides by πh
∵ 
∴ 
→ The coefficient of r² is 1, so switch the two sides
∴ 
The independent variable (x) is the domain
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