1)2lg5 + 1/2lg16 2)log4(13-x) = 2 3)log0.2(x^+4x)=-1 - вопрос №125121624132302412676567 от Некий2006 16.11.2021 06:16

Question

Математика: 1)2lg5 + 1/2lg16 2)log4(13-x) = 2 3)log0.2(x^+4x)=-1 решите. по фасту

Некий2006 · Answer

1) 2lg5 + 1/2lg16 = lg5^2 + lg16^(1/2) = lg25 + lg4 = lg100 = lg10^2 = 2
2) log_4_(13 - x) = 2
log_4_(13 - x) = log_4_16
13 - x = 16
x = -3
3) log_0.2_(x^2 + 4x) = -1
log_0.2_(x^2 + 4x) = log_0.2_5
x^2 + 4x = 5
x^2 + 4x - 5 = 0
D=16+20=36
X1=-5
X2=1