If the coefficients of (2r+1)th term and (r+2)th term in the expansion of (1+x)^43 are equal,then find r.?

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2006-11-06 22:48:57 · 4 answers · asked by squashu 1 in Science & Mathematics ➔ Mathematics

we know nCr-1 = nCn-r-1

now n = 43

so 2r +r + 1 = 43
or r= 14

2006-11-06 22:55:29 · answer #1 · answered by Mein Hoon Na 7 · 1⤊ 0⤋

C(43,2r) = C(43,r+1)
2r = 43- (r+1)
2r = 42 - r
3r = 42
r = 14

2006-11-06 22:59:19 · answer #2 · answered by Anonymous · 0⤊ 0⤋

T(2r+1)=43C2r
T(r+2)=43C(r+1)
given 43C2r=43C(r+1)
2r=43-(r+1)
3r=42
r=14

2006-11-06 23:01:50 · answer #3 · answered by raj 7 · 0⤊ 0⤋

(1 + 2r + 1)^43 = (1 + r + 2)^43
2r + 2 = r + 3
r = 1

2006-11-06 22:52:15 · answer #4 · answered by Dave 6 · 0⤊ 1⤋