c) \(\dfrac{2^3+2^4+2^5+2^6}{15^2}\)
\(=\dfrac{2^3\cdot\left(1+2+2^2+2^3\right)}{15^2}\)
\(=\dfrac{2^3\cdot15}{15\cdot15}\)
\(=\dfrac{2^3}{15}\)
\(=\dfrac{8}{15}\)
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c) \(\dfrac{2^3\left(1+2+2^2+2^3\right)}{15^2}=\dfrac{2^3.15}{15^2}=\dfrac{8}{15}\)
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