Bring (0,25) (2,9) into the equation and get:
25=b 1
9=2k+25
Solution: b 1=25, k=-8.
So: y= -8t+25.
(2) Since the two straight lines are parallel, the equation of the straight line after refueling is: y= -8t+b2.
Bring point (2, 30) into the equation:
2= -8x30+b2
Solution: b2=46, so the equation is y= -8t=46.
According to the meaning of the question: when y=0, bring it into the equation and get t=5.75 (hours).
(3) When t = 500 ÷ 100 = 5 (hours) is substituted into the equation, we get:
Y= -8x5+46=6 (length)