Select all the correct answers. Which vectors are unit vectors? U=(-1/3 sqrt(7/2),1/3sqrt(13/2))
U=(1/sqrt(3),-sqrt(2/3))
U=(1/2sqrt(5/3),-1/2sqrt(7/3))
U=(3/sqrt(7),-2/sqrt(7))
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Write the expression 7x^3-28xy^2 as the product of 3 factors

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! )

36x2 + 49y2 = 1,764 the foci are located at: (-√13, 0) and (√13,0) (0, -√13) and (0,√13) (-1, 0) and (1, 0)edit: the answer is (- the square root of 13, 0) and (the square root of 13, 0)