![1)2tg\frac{\pi }{3}*Ctg(-\frac{\pi }{6})+Cos\pi-2Sin\frac{\pi }{4}=2\sqrt{3}*(-\sqrt{3})-1-2*\frac{\sqrt{2}}{2}= -6-1-\sqrt{2}=-(\sqrt{2}+7)](https://tex.z-dn.net/?f=1%292tg%5Cfrac%7B%5Cpi%20%7D%7B3%7D%2ACtg%28-%5Cfrac%7B%5Cpi%20%7D%7B6%7D%29%2BCos%5Cpi-2Sin%5Cfrac%7B%5Cpi%20%7D%7B4%7D%3D2%5Csqrt%7B3%7D%2A%28-%5Csqrt%7B3%7D%29-1-2%2A%5Cfrac%7B%5Csqrt%7B2%7D%7D%7B2%7D%3D%20-6-1-%5Csqrt%7B2%7D%3D-%28%5Csqrt%7B2%7D%2B7%29)
2a) Sin124⁰ > 0
Cos203⁰ < 0
tg(- 280⁰) = - tg280⁰ < 0
( + ) * ( - ) * (- ) = ( + )
Знак выражения положительный
2б) ![Sin\frac{7\pi }{10} =Sin126^{o}>0\\\\Cos\frac{13\pi}{12}=Cos195^{o}<0\\\\(+)*(-)=(-)](https://tex.z-dn.net/?f=Sin%5Cfrac%7B7%5Cpi%20%7D%7B10%7D%20%3DSin126%5E%7Bo%7D%3E0%5C%5C%5C%5CCos%5Cfrac%7B13%5Cpi%7D%7B12%7D%3DCos195%5E%7Bo%7D%3C0%5C%5C%5C%5C%28%2B%29%2A%28-%29%3D%28-%29)
Знак выражения отрицательный
2) 15b-20c / 10b = 5(3b-4c) / 10b = 3b-4c / 2b
4) a-3b / a^2+3ab = a-3b / a(a+3b)
6) 3x^2+15xy / x+5y = 3x(x+5y) / x+5y = 3x
8) 5x-15y / x^2-9y^2 = 5(x-3y) / (x-3y)(x+3y) = 5 / x+3y
10) 6cb-18c^2 / (b-3c)^3 = 6c(b-3c) / (b-3c)^3 = 6c / (b-3c)^2
12) a^3-b^3 / a-b = (a-b)(a^2+ab+b^2) / a-b = a^2+ab+b^2
(-0,5a¹⁵b⁴)² · (-4/7ab⁷) = 0,25а³⁰b⁸ · (-4/7ab⁷) = 1/4a³⁰b⁸ · (-4/7ab⁷<span>) = -1/7a</span>³¹b¹⁵
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