In how many ways can seven books be arranged on a bookshelf?

Find the number of positive three-digit even integers whose digits are among 9, 8, 7,5, 3, and 1.

The first few steps in solving the quadratic equation 9x2 + 49x = 22 ? 5x by completing the square are shown. 9x2 + 49x = 22 ? 5x 9x2 + 54x = 22 9(x2 + 6x) = 22 which is the best step to do next to solve the equation by completing the square? 9(x2 + 6x + 3) = 25 9(x2 + 6x + 3) = 49 9(x2 + 6x + 9) = 31 9(x2 + 6x + 9) = 103

Solve this 364x-64x=300x and 12(x2–x–1)+13(x2–x–1)=25(x2–x–1)