Given that y=ln(7x)y = \ln(7x)y=ln(7x), find dydx\frac{dy}{dx}dxdy. Select the correct option:
A: dydx=1x\frac{dy}{dx} = \frac{1}{x}dxdy=x1
B: dydx=7x\frac{dy}{dx} = \frac{7}{x}dxdy=x7
C: dydx=17x\frac{dy}{dx} = \frac{1}{7x}dxdy=7x1
D: dydx=ln(7)\frac{dy}{dx} = \ln(7)dxdy=ln(7)
425 exam-style questions on OCR A Level Maths 1.7 Differentiation, covering 1.7.1 Derivative as gradient of the tangent, 1.7.2 Gradient of the tangent at a point, 1.7.3 Sketching the gradient function, 1.7.4 Second derivatives, 1.7.5 Second derivative as rate of change of gradient, 1.7.6 Convex, concave and points of inflection (A-level only), 1.7.7 Differentiation from first principles for powers of x, 1.7.8 Differentiation from first principles for sin x and cos x (A-level only), 1.7.9 Differentiating x^n, 1.7.10 Differentiating e^(kx) and a^(kx) (A-level only), 1.7.11 Differentiating trigonometric functions (A-level only), 1.7.12 Derivative of ln x (A-level only), 1.7.13 Tangents and normals, 1.7.14 Stationary points, 1.7.15 Increasing and decreasing functions, 1.7.16 Points of inflection (A-level only), 1.7.17 Product and quotient rules (A-level only), 1.7.18 Chain rule (A-level only), 1.7.19 Parametric and implicit differentiation (A-level only), 1.7.20 Constructing differential equations (A-level only), and 1.7 Differentiation. Each one has a worked solution and a mark scheme showing where the marks go.