trend lines and equations

[cspindley]

hi,

look @ the following:

there is an equation displayed: y = -7.5x * + 998

i wish to calculate what the value would be on the trend line for 40 (ie next

1 along) - i need to put it in a var not just to be able to see it

i also do not understand the equation, it bears little resemblance to the trend line drawn