2log5=xdan5log3=y nilai dari 15log20

2log5 = x
5log3 = y
2log3 = xy
15log20 = log20/ log15
=log2² x 5 / log 5 x 3
=log2² + log5 / log5 + log3
=(2 x 2log2) + 2log5 / 2log5 + 2log3
=(2 x 1) + x / x + xy
=2 + x / x (1 + y)