Заменим f(x) = z(t(x)) (t = x / 3) и возьмём производную сложной функции:
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![f'(x)=z'(t(x)) = ctg '(t(x))=-\frac{1}{\sin^2t(x)}\cdot t'(x)=-\frac{1}{3\sin^2(x/3)}](https://tex.z-dn.net/?f=f%27%28x%29%3Dz%27%28t%28x%29%29+%3D+ctg+%27%28t%28x%29%29%3D-%5Cfrac%7B1%7D%7B%5Csin%5E2t%28x%29%7D%5Ccdot+t%27%28x%29%3D-%5Cfrac%7B1%7D%7B3%5Csin%5E2%28x%2F3%29%7D)
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3) (m⁻⁴/(10n⁵k²))⁻² : (5m²n³k)³ = (10n⁵k²/m⁻⁴)² · (5m²n³k)⁻³
= 10² · n¹⁰k⁴m⁸ · 5⁻³ · m⁻⁶n⁻⁹k⁻³ = 100/125 · m⁽⁸⁻⁶⁾n⁽¹⁰⁻⁹⁾k⁽⁴⁻³⁾ = 4m²nk/5
4) (9c⁵/(a³b⁻²))⁻² : (a²b⁻³/(6c⁴))³ = (a³b⁻²/(9c⁵))² · (6c⁴/(a²b⁻³))³ =
= (a⁶b⁻⁹/(9²c¹⁰)) · (6³c¹²/(a⁶b⁻⁹)) = 1/81 · a⁶b⁻⁹c⁻¹⁰ · 216c¹²a⁻⁶b⁹ = 8/3 · a⁽⁶⁻⁶⁾b⁽⁹⁻⁹⁾c⁽¹²⁻¹⁰⁾ = 8c²/3
6, 2 сантиметров правильно или нет не знаю
A) 6-x(x+1)=9-x^2
6-x^2-x=9-x^2
-x^2-x+x^2=9-6
-x=3
x=-3
б) 6(x-2)=7x-(3x+1)
6x-12=7x-3x-1
6x-7x+3x=-1+12
2x=11
x=5,5