1. If y = x^2 + c is the equation of a curve, does this curve lie completely above the x-axis
a) c > 0
b) (1, 4) is a point on the curve
The primary requrirement for the curve to lie above the x-axis is that the Value Y is never negative. Lets look at the possible values of x that can make Y negative
a) X < 0 : X being negative does not impact Y because in the equation X is raised to a even power making the result positive. Now the total value of Y depends on C
b) X = 0 : C determines the value of Y
c) X >0 - Clearly no issues here as long as C is not negative enough to make the equation.
Therefore we need to answer if C is + or - number.
The option A clearly tells us that C is +. So that helps
The option B gives us values of X & Y, from which C can be calculated. => C = +3.
Answer: Either one by themselves is enough to solve the probelm