JAMB - Mathematics (2007 - No. 29)
If log102 = x, express log1012.5 in terms of x
2(1 + x)
2 + 3x
2(1 - x)
2 - 3x
Shpjegimi
log1012.5 = log10 121/2
= log1025/2
= log1025 - log102
= log1052 - log102
= 2log105 - log102
= 2log1010/2 - log102
= 2(1-x)- x
= 2 - 2x – x
= 2 – 3x
= log1025/2
= log1025 - log102
= log1052 - log102
= 2log105 - log102
= 2log1010/2 - log102
= 2(1-x)- x
= 2 - 2x – x
= 2 – 3x