જો left(x^{n}+frac{2}{x^{5}}right)^{7} ના દ્વ | vedclass

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Question

coefficients and there cumulative sum are :


	
		
			Coefficient
			Commulative sum
		
		
			$x ^{7 n } \rightarrow{ }^{7} C _{0}$
			$1$

Vedclass · Accepted Answer

$57$

Vedclass · Answer

coefficients and there cumulative sum are :


	
		
			Coefficient
			Commulative sum
		
		
			$x ^{7 n } ightarrow{ }^{7} C _{0}$
			$1$
		
		
			$x ^{6 n-5} ightarrow 2 \cdot{ }^{7} C _{1}$
			$1+14$
		
		
			$x ^{5 n -10} ightarrow 2^{2} \cdot{ }^{7} C _{2}$
			$1+14+84$
		
		
			$x ^{4 n -15} ightarrow 2^{3} \cdot{ }^{7} C _{3}$
			$1+14+84+280$
		
		
			$x ^{3 n -20} ightarrow 2^{4} \cdot{ }^{7} C _{4}$
			$1+14+84+280+560=939$
		
		
			$x ^{2 n -25} ightarrow 2^{5} \cdot{ }^{7} C _{5}$
			 
		
	


 

$3 n-20 \geq 0 \cap 2 n-25<0 \cap n \in I ~\ 	herefore \quad 7 \leq n \leq 12 ~\ 	ext { Sum }=7+8+9+10+11+12=57$

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