Section: Mathematical Reasoning

31) If 4x² - 7 = 9, what is the value of x³ + 2x?

1. 4
2. 8
3. 12
4. 16
5. 20

To solve this, you must first solve for x.

1. Add 7 to both sides:
   4x² = 16
   
2. Divide the 4 off:
   x² = 4
   
3. Square root both sides:
   x = 2
   

Now we need to solve for the other equation using the value of 2 for x

2³ + 2(2) = 12