4y^3+15y - 17y+y^3 = 5y^3 - 2y
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[2x²-5x-12=0 D=25+96=121 x1=(5-11)/4=-1,5 U x2=(5+11)/4=4∉[-π/2;π]
[2cosx+1=0⇒2cosx=-1⇒cosx=-1/2⇒x=-2π/3+2πn U x=2π/3+2πn⇒
x=2π/3∈[-π/2;π]
Ответ x=-1,5;x=2π/3
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