Explanation:
I cannot draw here, but I can give you the data, calculation and explanation.
10 months ago the snake was first discovered.
4 months ago it was 390 cm long.
right now (when they called for help) it is 500 cm long.
when they say "month", I assume they mean 30 days.
so, it took the snake 4 months (4×30 = 120 days) to grow from 390 cm to 500 cm.
that is 110 cm in 120 days = 11cm /12 days growth rate.
10 months ago (10×30 = 300 days) it was
300 × 11/12 cm shorter = 25×11 = 275 cm
so, it was 500 - 275 = 225 cm long.
you draw a graph with months on the x-axis (-10 to -3 to 0 3 to 4 to 12), and the y-axis I recommend to scale in meters (1 meter = 100 cm). and then you draw ac straight line from (-10, 2.25) to (0, 5).
in 3+1 months they will have caught the snake and caged it.
4 months are again 120 days.
if it keeps growing at the same rate, it would grow another 275 cm.
that would make it 775 cm long.
in this case the cage will not be big enough.
but if it will follow more or less the mean value of its species, then it will stop growing before reaching 700 cm and will fit into the cage.
if it keeps growing, in 1 year (12 months = 12×30 ÷ 360 days) it will be adding
360 × 11/12 = 30×11 = 330 cm
and have grown to 500 + 330 = 830 cm length.
in short. the function of the length of the snake is
f(x) = 11/12 x + 500
for x represents the months before now (negative) or in the future (positive).