SOLUTION: 1)log65+2log5-2log40 2)log4+10 log7-logy=1 find y

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: 1)log65+2log5-2log40 2)log4+10 log7-logy=1 find y      Log On


   

Question 981451: 1)log65+2log5-2log40
2)log4+10 log7-logy=1 find y
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
1)
log%2865%29%2B2log%285%29-2log%2840%29

log%2865%29%2Blog%285%5E2%29-log%2840%5E2%29

log%28%2865%2A25%29%29-log%281600%29

log%28%28%2865%2A25%29%2F1600%29%29

log%28%28%2865%2Across%2825%291%29%2Fcross%281600%2964%29%29

log%28%2865%2F64%29%29

2)
log%284%29%2B10+log%287%29-log%28y%29=1........... find y
log%284%29%2Blog%287%5E10%29-log%28y%29=1
log%284%2A7%5E10%29-log%28y%29=1........1=log%2810%29

log%28%28%284%2A7%5E10%29%2Fy%29%29=log%2810%29...since log same, we have

%284%2A7%5E10%29%2Fy=10

4%2A7%5E10=10y

y=%284%2A7%5E10%29%2F10

y=%282%2A7%5E10%29%2F5

y=%282%2A282475249%29%2F5

y+=+564950498%2F5