Moderate -0.8 This is a straightforward application of the chain rule to find dy/dx, evaluate at the given point, then use y - y₁ = m(x - x₁). The chain rule here is simple (power of a linear function), and all steps are routine with no problem-solving required. Easier than average for A-level.
Differentiate to obtain $k(4x+1)^{-\frac{1}{2}}$ | M1 | any non-zero constant $k$
Obtain $2(4x+1)^{-\frac{1}{2}}$ | A1 | or equiv, perhaps unsimplified
Obtain $\frac{2}{3}$ for value of first derivative | A1 | or unsimplified equiv
Attempt equation of tangent through $(2, 3)$ | M1 | using numerical value of first derivative provided derivative is of form $k'(4x+1)^n$
Obtain $y = \frac{2}{3}x + \frac{5}{3}$ or $2x - 3y + 5 = 0$ | A1 5 | or equiv involving 3 terms