MCQ
If $y = a{e^{mx}} + b{e^{ - mx}}$, then ${{{d^2}y} \over {d{x^2}}} - {m^2}y = $
  • A
    ${{m}^{2}}(a{{e}^{mx}}-b{{e}^{-mx}})$
  • B
    $1$
  • $0$
  • D
    None of these

Answer

Correct option: C.
$0$
c
(c) $y = a{e^{mx}} + b{e^{ - mx}};$ 

$\therefore \frac{{dy}}{{dx}} = am{e^{mx}} - mb{e^{ - mx}}$

Again $\frac{{{d^2}y}}{{d{x^2}}} = a{m^2}{e^{mx}} + {m^2}b{e^{ - mx}}$

==> $\frac{{{d^2}y}}{{d{x^2}}} = {m^2}(a{e^{mx}} + b{e^{ - mx}}) \Rightarrow \frac{{{d^2}y}}{{d{x^2}}} = {m^2}y$

or $\frac{{{d^2}y}}{{d{x^2}}} - {m^2}y = 0$.

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