X*9=81
X=81:9
X=9
Ответ: 9
Доказательство
Х*9=81
9*9=81
( X + 7 )^2 = 28X
X^2 + 14X + 49 = 28X
X^2 - 14X + 49 = 0
D = 196 - 196 = 0
X = 14 : 2 = 7
Ответ Х = 7
8=2³ = ((√2)²)³ = (√2)⁶
16=2⁴ = ((√2)²)⁴ = (√2)⁸
log₈ a³ = log(√₂)⁶ a³ = 3*(¹/₆) log√₂ a = ¹/₂ log√₂ a = log√₂ a^(¹/₂)
log₁₆ a = log(√2)⁸ a = ¹/₈ log√₂ a
<u>log√₂ a^(¹/₄) - log√₂ a^(¹/₂) </u>= <u>log√₂ (a^(¹/₄) : a^(¹/₂)) </u>=<u> log√₂ a^(⁻¹/₄) </u>=
¹/₈ log√₂ a ¹/₈ log√₂ a ¹/₈ log√₂ a
= ⁻<u>¹/₄ log√₂ a </u>= -¹/₄ * 8 = -2
¹/₈ log√₂ a
Ответ: -2
5-3(x-2(x-2x+4))=2
5-3(x-2(4-x))=2
5-3(x-8+2x)=2
5-3(3x-8)=2
5-9x+24=2
-9x=-27
x=3