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Mathematics

Find the square of:

2a1a2a -\dfrac{1}{a}

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Answer

(2a1a)2(2a - \dfrac{1}{a})^2

Using the formula

(∵ (x - y)2 = x2 - 2xy + y2)

=(2a)22×2a×1a+1a2=4a24aa+1a2=4a24+1a2= (2a)^2 - 2 \times 2a \times \dfrac{1}{a} + \dfrac{1}{a}^2\\[1em] = 4a^2 - \dfrac{4a}{a} + \dfrac{1}{a^2}\\[1em] = 4a^2 - 4 + \dfrac{1}{a^2}

Hence, (2a1a)2(2a - \dfrac{1}{a})^2 = 4a24+1a24a^2 - 4 + \dfrac{1}{a^2}

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