Question

If the line y=4x+3 is tangent to the curve y=x^2+c, then c is?

Answer 1

differentiate the curve y, we'll get the slope of tangent which is 2x=4.
so now we know that the tangent is at a point x=2 and y=4(2)+3=11.
Substituting the value of this point (2,11) into the curve equation,
11=2^2+c
thus c=7.
:)

Answer 2

how did you get 2x=4?

Answer 3

the gradient of tangent line is 4 meanwhile the slope of tangent is 2x.
they are the same :)

Answer 4

ohhh ok...Thank you! :)

Answer 5

welcome :)