If the rectangular screen of a computer monitor is designed to have a length of x inches, a perimeter of P inches and an area of A square inches, which of these equations must be true?
Choose the correct choice from the following answers:
A) x^2 + Px + A = 0
B) x^2 - Px - 2A = 0
C) 2x^2 + Px + 2A = 0
D) 2x^2 - Px - 2A = 0
E) 2x^2 - Px + 2A = 0
Notice that we can discard options A, and C right away. The sum of 3 positive values Cannot be 0.   Now, assume:   Length =x = 1 inchand width = 1 inch;   Perimeter =P = 4 inches;   Area =A = 1 square inches.   Plug the values of x, P, and A into the answer choices: only for E 2x^2 - Px  + 2= 
<gadget id="calculator"> + 2</gadget>
<output>2</output>
2 - 4 + 2= 
<gadget id="calculator">2 - 4 + 2</gadget>
<output>0</output>
0.   Answer: 2x^2 - Px + 2A= 0.
<result>E</result>
If the rectangular screen of a computer monitor is designed to have a length of x inches, a perimeter of P inches and an area of A square inches, which of these equations must be true?