Recent content by BillhB

Hey Mark, Thanks for the input, yeah I thought what I did was variation of parameters and couldn't make out some of the comments either. I'll talk to the professor. Thanks for the input and your time.

Hey, not really looking for authority, just wondering how to interpret the comments. I rework missed questions, but I don't really understand what I missed. I know I didn't justify everything, but like I said I didn't think there was a need to. It was a DE class, the justification for the...

My apologies, let me know if this is better. If not, I can type it all out just worried it'll lose context that way.

Err? My reasoning is already there. You solve a system of equations for ##u_1'## and ##u_2'##, take the integral of ##u_1'## and ##u_2'##, and bam ##y_p=y_1u_1+y_2u_2##, you're done. ##y_1## and ##y_2## are obtained from the homogeneous part. I'm really interested in interpreting the comments.

Homework Statement Use variation of parameters to solve ##\frac{d^2y}{dx^2} + 4y = sec(2x)## Homework Equations Really just curious about comments, see picture. The Attempt at a Solution I'm having a hard time deciphering the comments I got back on an exam. For the first comment, is there a...

Got it. Just worried about what other notation 'mistakes' I'm not aware of. Thanks though, appreciate all the comments and time you've spent replying.

Whoops, fixed it. Okay, but he seemed adamant that it was "wrong" notation. Terrible, terrible notation, garbage notation notes give that kind of vibe. Just a bit worried, have an exam in that class soon. Most of my quiz scores are abysmal due to notation I guess. To be fair, some it's...

No. It was just a simple separable differential equation.. $$\frac{dy}{dx}=\frac{1}{x}$$ $$\int{dy}=\int \frac{dx}{x}$$ $$y=ln|x| + C$$ It was just me writing out of a substitution for a Bernoulli Equation.. $$xy\frac{dy}{dx}+x^2-y^2=0$$ $$\frac{dy}{dx}-yx^{-1}=-xy^{-1}$$ so I had ##v=y^2##...

Is there some standardized math text with "proper universal notation" I could read for calculus? In one of my courses, $$\int\frac{dx}{x}$$ had a red mark through it, with a note that said "impossible" or something. I earned a zero on the question due to the above. In another instance...

Got it, thank you.

That is what I was assuming was the answer, but wasn't sure. Thanks. Any idea why they just didn't make the fractional charge the base constant?

Maybe so, but it still doesn't make sense why e wasn't just redefined. I don't get how we can say e is discrete, but continuous for elementary particles.

So why do Quarks have fractional non-discrete charge? Wouldn't it just be easier to just define ##\frac{1}{3}e## as +e and vice versa to preserve the discreetness of what we define as e?

Got you. Thanks.

I agree but I put when X = 0 m equaled the above ... when ##X \neq 0## m = -2 or m =6 and got points deducted with a red mark through the when X = 0 part? Wondering if something about above is wrong or if I need to go to professor and seek clarification for deduction.