已知2^a=3,4^b=5,8^c=7,求8^a+2b-c的值...thanks
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![已知2^a=3,4^b=5,8^c=7,求8^a+2b-c的值...thanks](/uploads/image/z/3925476-36-6.jpg?t=%E5%B7%B2%E7%9F%A52%EF%BC%BEa%3D3%2C4%EF%BC%BEb%3D5%2C8%EF%BC%BEc%3D7%2C%E6%B1%828%EF%BC%BEa%2B2b-c%E7%9A%84%E5%80%BC...thanks)
已知2^a=3,4^b=5,8^c=7,求8^a+2b-c的值...thanks
已知2^a=3,4^b=5,8^c=7,求8^a+2b-c的值...thanks
已知2^a=3,4^b=5,8^c=7,求8^a+2b-c的值...thanks
8^a=(2^3)^a=(2^a)^3=3^3=27
8^(2b)=(2^3)^2b=2^6b=4^3b=(4^b)^3=5^3=125
8^c=7,8^(-c)=1/(8^c)=1/7
8^(a+2b-c)=(8^a)(8^2b)(8^-c)=27×125÷7
回答的不对,算不出来,而且怎么会有8^(-C)呢