Which of the following are trigonometric identities?
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What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Find the value of x for which line a is parallel to line b

Julie goes to the sports store and spends $40.50 before tax. she buys a pair of shorts for $21.75 and 3 pairs of socks that each cost the same amount. how much does each pair of socks cost? $$