Question

A formula for the normal systolic blood pressure for a man age A, measured in mmHg, is given as

P = 0.006A2 − 0.02A + 120. Find the age to the nearest year of a man whose normal blood pressure measures 123 mmHg.

Answer 1

I think the equation should be
P(A) = 0.006A2 - 0.02A + 120

126 = 0.006A2 - 0.02A + 120

0 = 0.006A2 - 0.02A - 126+120

0=0.006A2 - 0.02A - 6

you can use the quadratic formula to solve for the man's age.
A = (-b ± sqrt[b2 - 4ac]) / (2a)
A = (0.02 ± sqrt[(-0.02)2 - 4(0.006)(-6)]) / (2*0.006)
A = (0.02 ± sqrt[0.1444]) / 0.012
A = 33.3, -30

Since age cannot be negative, your answer is 33 years old