MCQ
If $\text{f(x)}=\begin{cases}\text{ax}^2+\text{b},&0\leq\text{x}<1\\4,&\text{x}=1\\\text{x}+3,&1<\text{x}\leq2\end{cases}$ then the value of $(a, b)$ for which $f(x)$ cannot be continuous at $x = 1,$ is:
  • A
    $(2, 2)$
  • B
    $(3, 1)$
  • C
    $(4, 0)$
  • $(5, 2)$

Answer

Correct option: D.
$(5, 2)$
$\lim\limits_{\text{x}\rightarrow1^-}\text{f(x)}=\text{f}(1)$
$\lim\limits_{\text{x}\rightarrow1}\text{ax}^2+\text{b}=4$
$a + b = 4$
We have possible values as $(2, 2), (3, 1), (4, 0)$
But can not be $(5, 2).$
Function is can not be continuous at $(5, 2).$

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