Ответ:
1) 4*(5a-3b+c)-3*(2a-b-3c) = 20а–12b+4c–6a+3b+9c=
14а-9b+13c
2) (x-y)-(y-z)-(z+x)
=x-y-y+z-z-x=-2y
3) 2a*(3b-5c)-3c*(-3a+2b)+4b*(6a-2c) = 6ab-10ac+9ac-6cb+24ab-8bc = 30ab-ac-14bc
Sinx < -1/2
2π/3+2πn < x < 4π/3+2πn, n∈Z
x ∈(2π/3+2πn; 4π/3+2πn), n∈Z
Ускорение - это вторая производная от пути по времени.
x(t) = 3t² + 9lnt + 7
![x'(t)=3(t^{2})'+9(lnt)'+7'=6t+9*\frac{1}{t}=6t+\frac{9}{t}\\\\x''(t)=6(t)'+9(\frac{1}{t})'=6-\frac{9}{t^{2}}\\\\6-\frac{9}{t^{2} }=2\\\\\frac{9}{t^{2}}=4\\\\t^{2}=\frac{9}{4}\\\\t=1,5](https://tex.z-dn.net/?f=x%27%28t%29%3D3%28t%5E%7B2%7D%29%27%2B9%28lnt%29%27%2B7%27%3D6t%2B9%2A%5Cfrac%7B1%7D%7Bt%7D%3D6t%2B%5Cfrac%7B9%7D%7Bt%7D%5C%5C%5C%5Cx%27%27%28t%29%3D6%28t%29%27%2B9%28%5Cfrac%7B1%7D%7Bt%7D%29%27%3D6-%5Cfrac%7B9%7D%7Bt%5E%7B2%7D%7D%5C%5C%5C%5C6-%5Cfrac%7B9%7D%7Bt%5E%7B2%7D+%7D%3D2%5C%5C%5C%5C%5Cfrac%7B9%7D%7Bt%5E%7B2%7D%7D%3D4%5C%5C%5C%5Ct%5E%7B2%7D%3D%5Cfrac%7B9%7D%7B4%7D%5C%5C%5C%5Ct%3D1%2C5)