If x² + y² = 40 and xy = 6 find the value of (x - y)²

In simplified exponential notation, the expression a^2•a^-3•a 1/a 0

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )

What is the slope of the line passing through the points (3, 3) and (5, 7) ? 1. 2 2. 1/2 3. −2 4. −1/2