Consider the curve

MATHEMATICS · Multi-part · A Level · Mathematics · Differentiation · Differentiation

Problem

Consider the curve y=kxry=kx^{r}, defined for x>0x>0, that passes through the point (3,54)(3,54). The line tangent to the curve at this point intersects the yy-axis at (0,−6)(0,-6). Parts: (a) Using only the information provided, determine the slope of the tangent line at (3,54)(3,54) and explain your reasoning. (b) Express the derivative dydx\dfrac{dy}{dx} of y=kxry=kx^{r} in terms of kk, rr, and xx. (c) By equating your result from part (a) with the derivative evaluated at x=3x=3, derive an equation that relates kk and rr. (d) Combine the relation from part (c) with the fact that the curve passes through (3,54)(3,54) to solve simultaneously for kk and rr. Show all algebraic steps without skipping intermediate reasoning. (e) Verify that the resulting function satisfies both original geometric constraints.

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