Question

If the graph of quadratic polynomial $a x^{2}+ bx+c$ cuts negative direction of y-axis,then what is the sign of c?

Answer 1

SOLUTION :

Given : Graph of quadratic polynomial  f(x) = ax² + bx + c cuts negative direction of y -axis.  

Then, on putting  x = 0 , to find the point of  intersection on y -axis.

y = ax² + bx + c

y = a(0) + b(0) + c

y = 0 + 0 + c

y = c  

Since ,the point of intersection (0,c) is below  the x-axis because f(x) cuts negative direction of y -axis.

Hence,  the sign of c is negative . i.e c < 0.

HOPE THIS ANSWER WILL HELP YOU..

Answer 2

Any point on x-axis ha x=0

therefore, putting x=0 --

a(0)^2 +b(0) + c =y

c= y

hence sign of C is negative