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**PatternMan****Member**- Registered: 2014-03-08
- Posts: 199

y=kx then dy/dx = k

if y= x^4 + 1/x -6x

then dy/dx = d/dx(x^4) + d/dx(x^-1) etc

so differentiation sqrt(x) + 1/sqrt(x) w.r.t.x

d/dx(sqrt(x)) = 1/2sqrt(x), d/x(1/sqrt(x)) = ? I get -1/2x^-3/2 but the book says -1/(2xsqrt(x))

I really should learn to use Latex.

"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,496

hi PatternMan

I really should learn to use Latex.

Yes, that would help.

Put this as a single power of x

Now use the rule for differentiating powers (multiply by the old power and lower the power by 1)

which is what you have I can now see.

But the 'book' answer is the same:

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

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**PatternMan****Member**- Registered: 2014-03-08
- Posts: 199

Yes I didn't realize they were the same. I'm barely proficient with surds and indices.

"School conditions you to reject your own judgement and experiences. The facts are in the textbook. Memorize and follow the rules. What they don't tell you is the people that discovered the facts and wrote the textbooks are people like you and me."

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