Rút gọna) A = \(\frac{1}{2}\)+\(\frac{1}{2^2}\)+. . . + \(\frac{1}{2^{99}}\)b) B =\(\frac{1}{2}\) -- \(\frac{1}{2^2}\)+\(\frac{1}{2^3}\)-- \(\frac{1}{2^4}\)+. . ....
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Rút gọn
a) A = \(\frac{1}{2}\)+\(\frac{1}{2^2}\)+. . . + \(\frac{1}{2^{99}}\)
b) B =\(\frac{1}{2}\) -- \(\frac{1}{2^2}\)+\(\frac{1}{2^3}\)-- \(\frac{1}{2^4}\)+. . . + \(\frac{1}{2^{99}}\)+ \(\frac{1}{2^{100}}\)
Mk làm mẫu câu a nha
a, Có :
2A = 1+1/2+1/2^2+.....+1/2^98
A = 2A - A = (1+1/2+1/2^2+.....+1/2^98)-(1/2+1/2^2+......+1/2^99) = 1 - 1/2^99
Tk mk nha
nhân A với 2 rồi lấy 2A-A