FInals tomorrow and I dont understand how to find the X values at which f(x) = (-x^2+1)(x^-3) has a horizontal tangent. I got as far as 0=x^-2-3x^-4 using the product rule but I cant get any farther... please need help!

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Posts: 1269

FInals tomorrow and I dont understand how to find the X values at which f(x) = (-x^2+1)(x^-3) has a horizontal tangent. I got as far as 0=x^-2-3x^-4 using the product rule but I cant get any farther... please need help!

Posts: 1484

f(x) = (-x^2+1)(x^-3)

so (-2x)(x^-3)+(-x^2+1)(-3x^-4)

then set all that equal to zero. so it has horizontal tangents when x=0.

and when (-2x)(x^-3)=-(-x^2+1)(-3x^4)

so (-2x)(x^-3)+(-x^2+1)(-3x^-4)

then set all that equal to zero. so it has horizontal tangents when x=0.

and when (-2x)(x^-3)=-(-x^2+1)(-3x^4)

Posts: 1269

thanks what is the answeer you got'? and i dont understand the bottom

Posts: 1484

there's going to be a point when (-2x)(x^-3)=-(-x^2+1)(-3x^4). whenever this happens the tangent line will also equal zero.

Posts: 94

all you do is find the derivative of the function, and find the zeros for the derivative. this should give you the horizontal tangets of the orginal graph.

Posts: 1876

this but wrong...

so you find the deriv which is (-2x)(x^-3)+(-x^2+1)(-3x^-4)

then just set that equal to 0....**0 = (-2x)(x^-3)+(-x^2+1)(-3x^-4)**

then solve for x.. that is your answer

so you find the deriv which is (-2x)(x^-3)+(-x^2+1)(-3x^-4)

then just set that equal to 0....

then solve for x.. that is your answer

Posts: 481

Posts: 10182

pretty sure this is right.

Posts: 13214

Posts: 500

correct me if i'm wrong, but i don't think that has anything to do with the problem. interesting, though.

Posts: 1269

so i just took the finally and most likely failed it fuck my life haha i studied 12_plus hours this week

the class is not even an AP, its only college prep and now i think im failing it! great

any tips on math? i cant seem to connect the dots to figure out problems...

the way i have mistakenly learned math is just memorizing specific problems and how to do those. anyone else have the same problem?

the class is not even an AP, its only college prep and now i think im failing it! great

any tips on math? i cant seem to connect the dots to figure out problems...

the way i have mistakenly learned math is just memorizing specific problems and how to do those. anyone else have the same problem?

Posts: 4215

Oh my god looking at those equations make me feel sick to my stomach and remind me how great it is to not be in school anymore and how useless that shit was in the grand scheme of things anyway....at least - in my career.

Posts: 94

yeah i guess im in calc BC and i'm taking a final on AB calc right now so i guess i could help. if you were to give me the topics that your covering right now i could help you out.

calcs a bitch. i'm not gonna lie.

calcs a bitch. i'm not gonna lie.

Posts: 1425

You might hate me then, I'm a math major =], I think math is fun! As to whoever said they're taking AB, AB is pie, I hear BC is a bitch though.

Posts: 4215

No no...I don't hate you at all... in fact, I admire you. Thank god for people like you cause people like me are useless when it comes to this stuff....

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