№1
1) 5² * 5⁹ = 5¹¹
2) 2⁸ : 2⁴ = 2⁴
3) (3³)² = 3⁶
4) 4⁸ * 7⁸ = (4 * 7)⁸ = 28⁸
5) (х²)⁵ : х³ = х¹⁰ : х³ = х⁷
№2
1) (5m²y³ + 3m³y² -m) - (3m²y³ +2m + 3m³y²) =
= 5m²y³ + 3m³y² - m - 3m²y³ - 2m - 3m³y² = 2m²y³ - 3m
2) 3x² (b + 2x) - 2x(2b²x + x²) = 3x²b + 6x³ - 4x²b² - 2x³ =
= 3x²b - 4x²b² + 4x³ = x²(3b - 4b² + 4x) = x²(b(3 - 4b) + 4x)
№3
1) (-0.7a³b⁴c²)(-1.8a²bc³) = 1.26(abc)⁵
2)
3) (18x³y³ - 12x⁴y) : (6x³y) = 3y² - 2x
№4
(b³ - b²)(b³ + b²) - (1 + b²)(1 - b² + b⁴) = b⁶ - b⁴ - 1 + b² - b⁴ - b² + b⁴ - b⁶ =
= - 1 - b⁴ = -(1 + b⁴)
- (1 + 0.1⁴) = - (1 + 0,0001) = - 1,0001
№5
х(х + 2) - (х + 3)(х + 1) = 2х + 3
х² + 2х - х² - х - 3х - 3 = 2х + 3
- х - 3х - 3 = + 3
4х = - 6
х = - 1,5
Ответ: - 1,5.
<em>х кг весит арбуз</em>
<em>х/2 весит пол арбуза</em>
<em>3,5+х/2=х</em>
<em>7+х=2х</em>
<em>2х-х=7</em>
<em>х=7 кг весит арбуз</em>
<span>m(t) = m0·2</span><span>^(−t/T)</span>
<span>m0=200 <span>мг
</span></span><span>T=3 мин
</span>m(t) = <span>25 <span>мг
__________
t - ?
Подставляем в формулу </span></span><span>m(t) = m0·2<span>^(−t/T) </span>значения </span>m0, Т и m(t) :
<span>25 = 200·2</span><span><span>^(</span><span>− t/3)
</span></span>25 = 200/2<span>^(t/3)</span>
2<span>^(<span>t/3) = 200/25
</span></span>2<span>^(t/3) = 8</span>
2<span>^(<span>t/3) = 2³
</span></span><span>t/3 = 3
</span><span>t = 9
Ответ: 9 минут
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