Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Continuity and Differentiability

Question:

If the derivative of the function $f(x)=\left\{\begin{matrix}bx^2+ax+4;&x≥-1\\ax^2+b;&x<-1\end{matrix}\right.$ is everywhere continuous, then:

Options:

a = 2, b = 3

a = 1, b = 1

a = – 2, b = – 3

a = – 3, b = – 2

Correct Answer:

a = 1, b = 1

Explanation:

$LHL(-1)=RHL(-1)⇒b-a+4=a+b$

so $2a=4⇒a=2$

$LHD(-1)=RHD(-1)⇒2b(-1)+a=2a(-1)$

$⇒-2b+a=-2a$

so $3a=2b$

so $b=3$