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√60×√40×√90=√30×2×20×2×3×30=30×2×√60=60√4×4×3=60×4√3=240√3
Ответ:
5x^2-7x+1=0
a=5 b=-7 c=1
D=b^2-4ac=(-7)^2+4×5×1=49+20=69=8(3)
D>0 имеет 2 корня
x1,2=-b+-D/2
x1=7+8(3)/2=15(3)/2
X2=7-8(3)/2=-1(3)/2
<span> 2cos60°-tgп/4=2(1/2-2/2)=2 </span>· -1/2=-1