For what values of a and b is the line 3 x + y = b tangent to the curve y = a x^{2} when x = 5?

Question

ash2326 · Answer

@jolee 3x+y=b
Can you find the slope of this line?

anonymous · Answer

simple. 3.

anonymous · Answer

3 is final srry

ash2326 · Answer

think about it

anonymous · Answer

I tried 3=2ax is this wrong approach? (2ax by taking derivative of y=ax^2

ash2326 · Answer

$$3x+y=b$$
taking derivative w.r.t x
$$3+\frac{dy}{dx}=0$$
$$\frac{dy}{dx}=-3$$
which is the slope

anonymous · Answer

but according to form mx+b, shouldn't slope be 3

ash2326 · Answer

3x+y=b
y=-3x+b
y=mx+b
Comparing both
m=-3, b=b

anonymous · Answer

omg! what a stupid mistake of mine!! thank you

anonymous · Answer

so a would equal -3/10

ash2326 · Answer

yes, right

ash2326 · Answer

We know that tangent is at point x=5, 
from this find y coordinate of the point and then use the line equation to find b

anonymous · Answer

and do u know why we use radians in calc?

ash2326 · Answer

Suppose you have sin x, it's domain is real no.s
x=1, 2, 3, these all are radians
Using degrees in calculator, you have to convert them first