Verified answer

log(a) b = 1/log(b) a

log² (0.1) z = 9/log(z) 0.1 - 20

одз x > 0 z ≠ 1

log² (0.1) z = 9*log(0.1) z - 20

log(0.1) z = t

t² - 9t + 20 = 0

по теореме виета t = 4 и 5

1. t = 4

log(0.1) z = 4

z = (1/10)^4 = 1/10000

1. t = 5

log(0.1) z = 5

z = (1/10)^5 = 1/100000