1.
1)
2/(a-b)+2/(a+b)=(2*(a+b)+2*(a-b))/((a+b)*(a-b))=
(2a+2b+2a-2b)/(a²-b²)=4a/(a²-b²).
2)
(4a/(a²-b²)):(8a²/(a²-b²))=4a*(a²-b²)/(8a²*(a-b²))=4a/(8a²)=1/(2a)=1/(2*5)=
=1/10=0,1.
2.
l=πrα/180° l=2πr/5
α=180°*l/(π*r)
α=2*180°*l/(2πr)
α=360°*(2πr/5)/(2πr)
α=360°/5
α=72°.
3.
(6000-6000*10%/100%)=6000-600=5400.
(5400-5400*20%/100%)=5400-1080=4320 (руб).