Argument from the Negative

It's not a car? Must be aliens.

The Argument from Negative occurs when:

Example:

Cliff: That blurry trail camera picture is of a Bigfoot.

Matt: How can you say that? It could just as well be a bear.

Cliff: You can't prove that it's not a Bigfoot, so I'm calling it a Bigfoot.

Who has the burden of proof here? Also, this might be a good example of Occam's Razor.

Not a bear? Must be a 'squatch.

All winter with no summer makes Jack a dull boy.

Example: 

Summer is not the best season; therefore, winter must be the best season.

Notice how spring and autumn have been suspiciously omitted from the discussion?

Example: 

2+2≠5; therefore, 2+2=7.

Clearly, our arguer just wants to come to the conclusion that 2+2=7. Perhaps, they have an agenda and hope to make a lot of money off of this conclusion. 

Obviously, a plausible answer is not even being considered here.