Find the max value of 5t/ (2t^2 +7)

[brno17]

Find the max value of 5t/ (2t^2 +7)

I got answer as sqrt/3.5h

Tangent to curve y=x^3-6x^2+8x at pt A(3,-3) also intersect curve at another point B.
Solve pt B (x,y)

I did y'=3x^2 -12x +8
y'=3*3^2-12*3 +8
=27-36+8
=3
y=3x+b
-3=3(3)+b
b=-9

y=3x-9

I don't know what to do from there

And Solve for a b c y=ax^2+bx+c that passes through pt (2,19) and has horizontal tangent at (-1,-8)

I don't know how to do that either

 

[LCKurtz]

Find the max value of 5t/ (2t^2 +7)

I got answer as sqrt/3.5h

That doesn't make any sense.

Tangent to curve y=x^3-6x^2+8x at pt A(3,-3) also intersect curve at another point B.
Solve pt B (x,y)

I did y'=3x^2 -12x +8
y'=3*3^2-12*3 +8
=27-36+8
=3

Check that last step. I don't get 3

y=3x+b
-3=3(3)+b
b=-9

y=3x-9

I don't know what to do from there

Fix it, then set the y's equal to see what x's work.