Urgent equation. I keep getting the wrong answer!

Question

P=21+Q²-4Q 

 

If Q= -2.5, what is P?

 

Please show working and explain.

Answer 1

P = 21+(-2.5)²-4(-2.5)

P = 21+6.25+10

P = 37.25

Answer 2

P = 21 + Q² - 4Q

 

When Q = -2.5:

 

P = 21 + (-2.5)² - 4*(-2.5)

 

The correct order to perform these operations is PEMDAS:

1. P = operations within parentheses
2. E = Exponents
3. M = Multiplications
4. D = Divisions
5. A = Additions
6. S = Subtractions

 

We have no operations inside of parentheses (P), so the first operation to perform is the exponent (E), (-2.5)² = (-2.5)*(-2.5) = 6.25:

 

P = 21 + 6.25 - 4*(-2.5)

 

The next operation to perform is the multiplication, 4*(-2.5) = -10:

 

P = 21 + 6.25 - (-10)

P = 21 + 6.25 + 10

 

Now do the additions:

 

P = 37.25