数学对数涵数运算急

1个回答

  • (1)原式=(1/2)*[log2 (7/48)] - (1/2)*(log2 42)+ (log2 12)

    =(1/2)*[log2 (7/48) - (log2 42)]+ (log2 12)

    =(1/2)*{log2 [(7/48)÷42]} + (log2 12)

    =(1/2)*{log2 [1/(6*48)]} + (log2 12)

    =-(1/2)*[log2 (4*9*8)] + 2+(log2 3)

    =-(1/2)*(5+ log2 9)+ 2+(log2 3)

    =(-5/2) - (log2 3)+ 2+(log2 3)

    =-1/2

    (2)原式=2lg5 + 2lg2+ lg5*(2lg2 + lg5)+(lg2)²

    =2+ (lg5)²+2*lg5*lg2+(lg2)²

    =2+(lg5+lg2)²

    =2+1=3