please help me with this I will mark as brainliest

Answer: 1. linear
2. quadratic
3. linear
4. linear
5. quadratic
6. quadratic
7. linear
Step-by-step explanation:
1. pi and d are constants, so linear.
2. quadratic since (x+3)^2
3. 3^2 is a constant since 3^2=9. x is also a constant, so linear.
4. x is a constant, so linear.
5. Quadratic since the equation's highest degree is 2.
6. Quadratic ==> x(x+3)=x^2+3x
7. 3x and -2 are constants, so linear.