Question

$(1 - log_{7}(28) )(1 - log_{4}(28) )$
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Answer 1

$(1-log_{7}28)(1-log_{4}28) =(1-log_{7}(4*7))(1-log_{4}(4*7))=(1-log_{7}4-log_{7}7)(1-log_{4}4-log_{4}7)=(1-log_{7}4-1)(1-1-log_{4}7)=-log_{7}4*(-log_{4}7)=1$