Question

a bamboo plant is growing 1 foot per day. when you first measure it, it is 4 feet tall.

a. write an equation to describe the height y, in feet, of the bamboo plant x days after you measure it.
would it be: x+y=4?

b. what is the y intercept?

Answer 1

would it be: x+y=4?

This is clearly this not correct if you put numbers into the equation. If y is the height after 10 days then the height is the plant is

10+y=4

so y=-6 or 6ft below ground!

The correct equation is

y=4+x

where both y and x are in feet. This agrees with the description as at time zero, x=0, the y=4 i.e 4ft. After 10 days the plant will be
y=4+10 = 14 or 14 ft tall. Which is a sensible value.

If we compare the equation with the general equation for a straight line which is

y=mx+c

where
m=gradient and
c=the y intercept

we see that m=1 and
c=4 (or the line passes through (0,4)