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# The sequence , , , . . ., has the property that for all . If , then determine

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The sequence , . . ., has the property that  for all . If , then determine

Guest Jan 31, 2015

#1
+20680
+10

The sequence , . . ., has the property that  for all .

If , then determine

$$\small{\text{  \begin{array}{rcrcrcr} x_{11}&=& x_{10}+x_{9} &=& (x_9+x_8)+x_9 &=& 2x_9+x_8\\ &=& 2x_9+x_8 &=& 2(x_8+x_7)+x_8 &=& 3x_8+2x_7\\ &=& 3x_8+2x_7 &=& 3(x_7+x_6)+2x_7 &=& 5x_7+3x_6\\ &=& 5x_7+3x_6 &=& 5(x_6+x_5)+3x_6 &=& 8x_6+5x_5\\ &=& 8x_6+5x_5 &=& 8(x_5+x_4)+5x_5 &=& 13x_5+8x_4\\ &=& 13x_5+8x_4 &=& 13(x_4+x_3)+8x_4 &=& 21x_4+13x_3\\ &=& 21x_4+13x_3 &=& 21(x_3+x_2)+13x_3 &=& 34x_3+21x_2\\ &=& 34x_3+21x_2 &=& 34(x_2+x_1)+21x_2 &=& 55x_2+34x_1\\ \end{array}  }}\\ \small{\text{x_{11} = 55x_2+34x_1}}$$

$$\small{\text{ \begin{array}{rcl} 55x_2+34x_1 -x_1 &=& 99 \\ 55x_2 +33x_1&=&99 \quad | \quad :11 \\ \boxed{5x_2+3x_1 = 9} \end{array}  }}$$

$$\small{\text{  \begin{array}{rcrcr} x_3 &=& &=& x_2+x_1 \\ x_4 &=& x_3+x_2 &=& 2x_2+x_1 \\ x_5 &=& x_4+x_3 &=& 3x_2+2x_1 \\ x_6 &=& x_5+x_4 &=& 5x_2+3x_1 \\ \end{array}  }}\\ \small{\text{x_6= 5x_2+3x_1 }}=9$$

heureka  Feb 1, 2015
#1
+20680
+10

The sequence , . . ., has the property that  for all .

If , then determine

$$\small{\text{  \begin{array}{rcrcrcr} x_{11}&=& x_{10}+x_{9} &=& (x_9+x_8)+x_9 &=& 2x_9+x_8\\ &=& 2x_9+x_8 &=& 2(x_8+x_7)+x_8 &=& 3x_8+2x_7\\ &=& 3x_8+2x_7 &=& 3(x_7+x_6)+2x_7 &=& 5x_7+3x_6\\ &=& 5x_7+3x_6 &=& 5(x_6+x_5)+3x_6 &=& 8x_6+5x_5\\ &=& 8x_6+5x_5 &=& 8(x_5+x_4)+5x_5 &=& 13x_5+8x_4\\ &=& 13x_5+8x_4 &=& 13(x_4+x_3)+8x_4 &=& 21x_4+13x_3\\ &=& 21x_4+13x_3 &=& 21(x_3+x_2)+13x_3 &=& 34x_3+21x_2\\ &=& 34x_3+21x_2 &=& 34(x_2+x_1)+21x_2 &=& 55x_2+34x_1\\ \end{array}  }}\\ \small{\text{x_{11} = 55x_2+34x_1}}$$

$$\small{\text{ \begin{array}{rcl} 55x_2+34x_1 -x_1 &=& 99 \\ 55x_2 +33x_1&=&99 \quad | \quad :11 \\ \boxed{5x_2+3x_1 = 9} \end{array}  }}$$

$$\small{\text{  \begin{array}{rcrcr} x_3 &=& &=& x_2+x_1 \\ x_4 &=& x_3+x_2 &=& 2x_2+x_1 \\ x_5 &=& x_4+x_3 &=& 3x_2+2x_1 \\ x_6 &=& x_5+x_4 &=& 5x_2+3x_1 \\ \end{array}  }}\\ \small{\text{x_6= 5x_2+3x_1 }}=9$$

heureka  Feb 1, 2015
#2
+92674
+3

Very nice, heureka......the additions on the right hand side are numbers in the Fibonacci series..!!!

CPhill  Feb 1, 2015