This question seems a little silly, because it looks so simple(adsbygoogle = window.adsbygoogle || []).push({});

but

There's one thing I don't understand:

If y`` +p(x)y` + q(x)y=0 ...equation 1.

and you have this equation:

u``y1 + u`(2y`1+py1) + u(y``1+py`1+qy1)=0 ....equation 2

and y1 is a solution of equation 1

then why is "u" gone in equation 1?

:P

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# Seems a little silly

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