27,3954≈27,40
27,3954≈27,4
27,3954≈39
381.
в)
![\sqrt[10]{1024} = 2 \\ 1024=2 ^{10} \\ 1024=1024](https://tex.z-dn.net/?f=%20%5Csqrt%5B10%5D%7B1024%7D%20%3D%202%20%5C%5C%201024%3D2%20%5E%7B10%7D%20%5C%5C%201024%3D1024%20%20)
г)
![\sqrt[3]{-343}=-7 \\ -343=(-7) ^{3} \\ -343=49*(-7) \\ -343=-343](https://tex.z-dn.net/?f=%20%5Csqrt%5B3%5D%7B-343%7D%3D-7%20%5C%5C%20%20%0A-343%3D%28-7%29%20%5E%7B3%7D%20%20%5C%5C%20%0A-343%3D49%2A%28-7%29%20%5C%5C%20-343%3D-343)
383.
в)
![\sqrt[5]{-32}= \sqrt[5]{(-2) ^{5} }=-2](https://tex.z-dn.net/?f=%20%5Csqrt%5B5%5D%7B-32%7D%3D%20%20%5Csqrt%5B5%5D%7B%28-2%29%20%5E%7B5%7D%20%7D%3D-2)
г)
![\sqrt[3]{64}= \sqrt[3]{ 4^{3} } =4](https://tex.z-dn.net/?f=%20%5Csqrt%5B3%5D%7B64%7D%3D%20%5Csqrt%5B3%5D%7B%204%5E%7B3%7D%20%7D%20%20%3D4)
384.
в)
![\sqrt[3]{ -\frac{27}{8} } = \sqrt[3]{ -(\frac{3}{2})^{3} } = -\frac{3}{2}=-1,5](https://tex.z-dn.net/?f=%20%5Csqrt%5B3%5D%7B%20-%5Cfrac%7B27%7D%7B8%7D%20%7D%20%3D%20%5Csqrt%5B3%5D%7B%20-%28%5Cfrac%7B3%7D%7B2%7D%29%5E%7B3%7D%20%20%7D%20%3D%20-%5Cfrac%7B3%7D%7B2%7D%3D-1%2C5%20)
г)
![\sqrt[4]{ \frac{81}{256} }= \sqrt[4]{ \frac{9 ^{2} }{16 ^{2} } }= \sqrt[4]{ \frac{3 ^{4} }{ 4^{4} } }= \frac{3}{4}=0,75](https://tex.z-dn.net/?f=%20%5Csqrt%5B4%5D%7B%20%5Cfrac%7B81%7D%7B256%7D%20%7D%3D%20%20%5Csqrt%5B4%5D%7B%20%5Cfrac%7B9%20%5E%7B2%7D%20%7D%7B16%20%5E%7B2%7D%20%7D%20%7D%3D%20%5Csqrt%5B4%5D%7B%20%5Cfrac%7B3%20%5E%7B4%7D%20%7D%7B%204%5E%7B4%7D%20%7D%20%7D%3D%20%5Cfrac%7B3%7D%7B4%7D%3D0%2C75%20)
385.
в)х³+4=0
х³=-4
x=-∛4
г) не видно
386.
в) x⁶-64=0
(х³-8)(х³+8)=0
(х-2)(х²+2х+4)(х+2)(х-2х+4)=0
х-2=0
х=2
х+2=0
х=-2
или
х⁶-64=0
(х³)²-64=0
(х³-8)(х³+8)=0
х³=8
х=∛8
х=2
х³+8=0
х³=-8
х=∛-8
х=-2
г)х⁵=3
![x= \sqrt[5]{3}](https://tex.z-dn.net/?f=%20x%3D%20%5Csqrt%5B5%5D%7B3%7D%20)
387.
в) 0,02х⁶-1,28=0
0,02(х⁶-64)=0
х⁶-64=0
(х³)²-64=0
(х³-8)(х³+8)=0
х³=8
х=∛8
х=2
х³+8=0
х³=-8
х=∛-8
<span>х=-2
</span>г) 51/4-3/4х²=0
1/4(51-3х²)=0
51-3х²=0
3х²-51=0
3(х²-51/3)=0
х²-17=0
(х-√17)(х+√17)=0
х-√17=0
х=√17
х+√17=0
х=-√17
А)
х=15*40/10=60
б)
х=4,2*6/3,6=42/6=7
в)
х=3*1*8/3*4=2
г)
х=4/3*6/4=2
д)
х/3,80=1
х=3,80
1. 6sin^2x-5+5cosx=0
6(1-cos^2x)+5cosx-5=0
6-6cos^2x+5cosx-5=0
-6cos^2x+5cosx+1=0
cosx=t
-6t^2+5t+1=0
D=b^2-4ac D=25-4*(-6)*1=49sx
t12=(-5+-7)/(-12) t1=1 t2=-1/6
cosx=1 x=2πn, n∈Z
cosx=-1/6 x= +-(π-arccos1/6)+2πn, n∈Z
sin2x+sin6x=2sin4xcos2x
sin4x=2sin2xcos2x=4sinxcosx(cos^2x-sin^2x)
cos50+sin80=cos(90-40)+sin80=sin40+sin80=2sin60cos20=√3cos20