What did Turner suggest as possible new frontiers?

The Frontier thesis was formulated 1893, when American historian Frederick Jackson Turner theorized that the availability of unsettled land throughout much of American history was the most important factor determining national development.

Explanation:

the idealization of the rural landscape ; admiration for the beauty of nature ; focus on an individual's inner concerns

for this case we have the following equation:

we apply distributive property to the terms within parentheses.

subtracting 2 on both sides of the equation: