21. 5(16v^2 -25)
5(4v + 5)(4v-5)
22. (3y + 5)(3y-5)
23. (3m - 1)^2
24. 4(9n^2 - 12n + 4)
4(3n - 2)^2
25. Doesn't look like there's much to factor... 3(3k^2 - 10k)
26. (n - 9)(n - 8)
27. (3a - 8)(a + 7)
28. 5(7r+5)(r+3)
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7.7m answers