Need help with derivative question

[linapril]

I've solved half the question (I think), but then gotten stuck... Can someone help me out?

The question:
The tangent to the curve y=ae^2x + bx on the point (0,4) has the gradient k=3. Determine the values of a and b.

My solution:
y' = 2ae^2x+b
y'(0) = 3
2ae²⁽⁰⁾+b)=3
2a+b=3
b=3-2a

And this is where I don't know how to proceed...
Would appreciate some help!

 

[MarkFL]

You have correctly done the hard part of differentiation. (Sun)

You also know $y(0)=4$. This will give you a second equation in the two unknowns, and then you will be able to determine the solution.