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標題:
e^x + e^(-x) = 3 ,x =?
e^x + e^(-x) = 3 ,x =? 因為諗左好耐都唔識計 希望有人可以step by step 咁講點計
最佳解答:
e^x + e^(-x) = 3 設 e^x = y 則e^(-x) = 1/(e^x) = 1/y y + 1/y = 3 y^2 + 1 = 3y y^2 - 3y + 1 = 0 y = [3 +/- √(9 - 4)]/2 y = (3 + √5)/2 or (3 - √5)/2 e^x = (3 + √5)/2 or (3 - √5)/2 x = In (3 + √5)/2 or In (3 - √5)/2 x = 0.9624 or -0.9624
其他解答:
e^x + e^(-x) = 3 ,x =?
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發問:e^x + e^(-x) = 3 ,x =? 因為諗左好耐都唔識計 希望有人可以step by step 咁講點計
最佳解答:
e^x + e^(-x) = 3 設 e^x = y 則e^(-x) = 1/(e^x) = 1/y y + 1/y = 3 y^2 + 1 = 3y y^2 - 3y + 1 = 0 y = [3 +/- √(9 - 4)]/2 y = (3 + √5)/2 or (3 - √5)/2 e^x = (3 + √5)/2 or (3 - √5)/2 x = In (3 + √5)/2 or In (3 - √5)/2 x = 0.9624 or -0.9624
其他解答:
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