Integration - Definite Integration as the Reverse of Differentiation

Integration - Definite Integration as the Reverse of Differentiation

Secondary 4
8 marks
  1. It is given that \(y=x^2\sqrt{2x-5}\), whose natural real domain is \(x\ge h\). Show that \(\frac{dy}{dx}=\frac{kx(x-2)}{\sqrt{2x-5}}\), where \(k\) is an integer and determine the value of \(h\) and of \(k\).[4]
  2. Hence evaluate \(\displaystyle \int_{3}^{7}\left\{\frac{10x(x-2)}{\sqrt{2x-5}}+6\right\}\,dx\).[4]

The derivative formula in part (a) applies for \(x>h\); the function is defined at \(x=h\), but its finite derivative is not.

Solution:

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Answer:\(h=\frac{5}{2},\ k=5\) \((b)\ \displaystyle\int_3^7\left\{\frac{10x(x-2)}{\sqrt{2x-5}}+6\right\}\,dx=300\)

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