Question

If graph of quadratic polynomial ax² + bx + c cuts positive direction of y-axis, then what is the sign of c?

Answer 1

If graph of quadratic polynomial `f(x)=ax^2 + bx + c` cuts positive direction of y-axis, then

Put x = 0 for the point of intersection of the polynomial and y-axis

We have `y = 0+0+c+c`

Since the point `(0,c)` is above the x-axis

Hence, the sign of c is positive, that is `c > 0`