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If $y = 8e^{9x}+6e^{-9x},$ then which of the following is the value of $\frac{d^2y}{dx^2}$ ? |
$35 y$ $81 y$ $-42 y $ $245 y$ |
$81 y$ |
The correct answer is Option (2) → $81 y$ $\frac{dy}{dx}=\frac{d(8e^{9x}+6e^{-9x})}{dx}=72e^{9x}-54e^{-9x}$ $\frac{d^2y}{dx^2}=9×72e^{9x}+45×9e^{-9x}$ $=81(8e^{9x}+6e^{-9x})=81y$ |
