Question

The following figure shows the graph of `f(x) =ax^(2)+bx +c`, then find the sign of values of `a, b and c`.

Answer 1

From the graph, `f(0) = c lt 0` (as the graph intersects the y-axis on the negative side)
Also the graph is concave upward `rArr a gt 0`
Further the vertex lies on the left-hand side of the y-axis.
So the abscissa or the vertex `- (b)/(2a) lt 0`
`rArr b gt 0 `(as `a gt 0`)