1)Notam cu X distanta totala a drumului.Cu A notam distanta parcursa in prima zi, cu B distanta parcursa a 2-a zi, cu C distanta parcursa a 3-a zi.
A=X/4
B=9X/20
C=18
A+B+C=X
X=X/4+9X/20+18
Aducem la acelasi numitor: 20X=5X+9X+360
6X=360⇒X=60
Cum X=60⇒A=15,B=27,C=18
2)
a)70*90=6300m sarma
b)Daca 4m sarma = 30g, atunci 1m sarma = 7.5g⇒6300m sarma=47.25 Kg
c)47.25*8.5=401.625lei
3)
x(1-√2)≥4-2√8
x(1-√2)≥4-4√2
x≤(4-4√2)/(1-√2)
x≤(4√2-4)/(√2-1)
x≤(4√2-4)(1+√2)
(4√2-4)(1+√2)=-4-4√2+4√2+8=4⇒
⇒x≤4