The wife and I were doing homework together, and we noticed something really strange when charting quadratics with a TI-series graphing calculator:
f(5) = -x^2 + 110x - 1000 f(5) = -5^2 + (110*5) - 1000 f(5) = -25 + 550 - 1000 f(5) = -475 // Wait a minute... -5^2 = -25 // Negative?
We knew this wasn't right, so we tried the formula out on an online calculator, and we got the same result:
So we decided to wrap the coefficient in parentheses, and it worked as expected:
// Wrap in parentheses... (-5)^2 = 25 // Positive, as expected
Obviously, I think the second solutions must be correct... but I can't imagine that in today's day and age, I have to explicitly wrap every negative coefficient in parentheses to ensure proper evaluation on a calculator. Is this the case, or is the first evaluation actually correct?
Thanks for taking the time!