Question

Differentiate y=x^3. Hence find to points on y=x^3+6 where the tangent has gradient 75....

Answer 1

two* :):)

Answer 2

so could you differentiate
y=x^3
?

Answer 3

yes 3x^2

Answer 4

gradient of tangent at a point is the derivative of the curve at that point
so,
75 = 3x^2
will give you 2 values of x co-ordinate where the gradient of tangent is 75

Answer 5

So then i just put the x points back into the original equation to get the y points????????

Answer 6

find 2 values of x first!
then plug them in
y=x^3+6

to get 2 y co-ordinates

hence u get 2 points

Answer 7

Sorry.....struggling to find the two x point....................

Answer 8

75 =3x^2
x^2 =25
x = \(\pm ???\)

Answer 9

+or - 5.............sorry made a dumb mistake

Answer 10

no problem :)
plug in x=+5 in y=x^3+6
find y

then plug in x=-5 in y=x^3+6
find y

and you get your 2 points :)

Answer 11

thanks heaps again...........life saver...........(-5,-119), (5,131)

Answer 12

those are correct :)
most welcome ^_^