Не могу решить задания:1) log5 150 - log5 3 + log5 1/2 - log5 12)10^2-3lg 53)Упростить...

1)log₅150-log₅3+log₅1/2-log₅1=log₅(150:3)+log₅1/2-0=log₅50+log₅1/2==log₅(50*1/2)=
log₅25=2
2)
$10^{2+3lg5}=10^{2}*(10^{lg5})^{3}=100*5^{3}=12500 \\ 3) \frac{2a^{2}+5a-12}{20-3} -a+1= \frac{2a^{2}+5a-12}{17} -a+1= \frac{2a^{2}+5a-12+17*(-a+1)}{17} = \\ \frac{2a^{2}+5a-12-17a+17}{17} = \frac{2a^{2}-12a+5}{17} \\$