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Mathematics 8 Online
OpenStudy (anonymous):

Calculus help please. Attachment inside

OpenStudy (anonymous):

i need help with 1b and 6

OpenStudy (danjs):

k

OpenStudy (danjs):

move the denominators to the top and make them negative exponents, then just use the normal power rule

OpenStudy (anonymous):

x^-4 +5x^-5

OpenStudy (danjs):

\[\frac{ d }{ dx }[x ^{-4}] + 5*\frac{ d }{ dx }[x ^{-5}]\]

OpenStudy (danjs):

yep, and the derivative of a sum, is the sum of the derivatives

OpenStudy (anonymous):

-4x^-5 -25x^-6

OpenStudy (danjs):

yep, not just fix those negative exponents on the final answer

OpenStudy (anonymous):

okay thanks can we move onto 6 ?

OpenStudy (danjs):

sure

OpenStudy (anonymous):

the derivative for 6 is 3x

OpenStudy (danjs):

The 'normal' will be perpendicular to the tangent at that point on the curve

OpenStudy (danjs):

y = x^3 + 1 at point (1,2) Find the Normal at the point.

OpenStudy (danjs):

\[\frac{ dy }{ dx } = 3x^2\]

OpenStudy (anonymous):

okay do i plug in 1 ?

OpenStudy (danjs):

The derivative dy/dx tells you the slope of the tangent line at any point, so if you plug in x=1, the slope of the tangent is 3(1)^2 = 3 right

OpenStudy (danjs):

Do you remember what the slope of the line perpendicular to that tangent line will be?

OpenStudy (anonymous):

?

OpenStudy (danjs):

Slope of the tangent at x=1 ....3 Slope of the normal at x=1, .....-1/3 The slope of the normal will be the negative reciprical of the slope of the tangent

OpenStudy (anonymous):

oh ya

OpenStudy (danjs):

So just make a line equation with , slope m=-1/3 and through point (1,2)

OpenStudy (danjs):

y - y1 = m(x-x1)

OpenStudy (anonymous):

y-2=-1/3(x-1)

OpenStudy (danjs):

yep, if you want to see graph y = x^3 + 1 and the line of the tangent (slope = 3 ) point (1,2) and the line of the normal you just found should be two perpendicular lines at that point

OpenStudy (danjs):

Here it is

OpenStudy (danjs):

Any other ones, or you good

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