A function is defined by $\displaystyle f(x) = x^2+2x+c$. Find the value of the constant c for which the range of f is given by f(x)≥ 3
The answer to the question you posted is c = 4, not $\displaystyle c \geq 4$. That is what my previous reply said. Stroodle made a small misunderstanding of the question: It is required that -1 + c = 3. This misunderstanding should have been clear to you given everything else said in that reply.