Agree with Iobo that m is the slope of the tangent line and b is the y-intercept of the tangent line. However, I would just add what the actual values are when applied to the parabola and its tangent you cited.
In this case, y' = 6x + 4 means that y'(2) = 16. So the the slope of the tangent line at x=2 is m=16.
To find b, the y-intercept of the tangent line, just use y=mx+b, your point (2,22) as (x,y), and m=16:
That gives 22 = 16(2) + b, or b = -10. Thus the equation of the tangent line to the parabola is y = 16x - 10.
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As always, if you need more help, please clarify where you are in the process and what's giving you trouble. I'd be more than happy to continue to assist.
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