標題:
exponential functions f.4 10pt
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發問:
in the following equations, (i)find the value of (11/5)^x and (ii)solve them (1) (11/5)^x-(5/11)^x=4 (2) (11/5)^x-(5/11)^x=-6
最佳解答:
1 i) (11/5)x - 1/[(11/5)x] = 4 (11/5)2x - 1 = 4[(11/5)x] (11/5)2x - 4[(11/5)x] - 1 = 0 (11/5)x = 1 + √5 or 1 - √5 (rejected) ii) (11/5)x = 1 + √5 x log (11/5) = log (1 + √5) x = 1.49 2 i) (11/5)x - 1/[(11/5)x] = -6 (11/5)2x - 1 = -6[(11/5)x] (11/5)2x + 6[(11/5)x] - 1 = 0 (11/5)x = - 3 + √10 or - 3 - √10 (rejected) ii) (11/5)x = - 3 + √10 x log (11/5) = log (- 3 + √10) x = -2.31
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