CUET Preparation Today
CUET
-- Mathematics - Section B1
Continuity and Differentiability
If $\frac{d}{dx}[ax^3+ ax^2 + ax + 1] = 9x^2 + 6x +3$, then $a$ is equal to
1
2
3
4
The correct answer is Option (3) → 3
$\frac{d}{dx}[ax^{3}+ax^{2}+ax+1]=3ax^{2}+2ax+a$
$3ax^{2}+2ax+a=9x^{2}+6x+3$
$\Rightarrow\;3a=9,\;2a=6,\;a=3$
$a=3$