Friday, 20 December 2013

SEQUENCE AND SERIES A7


Find the sum of the 1st six terms of the geometrical progression 4+16+64+…….

Solution

G1 = 4, r=4, n=6

Sn = G1(rn-1)/ r-1
             

S6 = 4(46-1)/4-1
             

S6 = 4(46-1)/3 
             

S6 = 4(4096-1)
             3

S6 = 4(4095)
             3

S6 = 4(4095)1365
             31

S6 = 4 x 1365
            

S6 = 5460


Hence the sum of the 1st six terms is 5460.
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