its (a) because (a) is C(x)=3x4+30x and 9+21 is 30 so its 3x2+30
11. x² - 7x = 0
x(x) - x(7) = 0
x(x - 7) = 0
x = 0 or x - 7 = 0
+ 7 + 7
x = 7
Solution Set: {0, 7}
12. 3x² - 4x = 20x + 27
+ 4x + 4x
3x² = 24x + 27
3x² - 24x - 27 = 0
x = -(-24) ± √((-24)² - 4(3)(-27))
2(3)
x = 24 ± √(576 + 324)
6
x = 24 ± √(900)
6
x = 24 ± 30
6
x = 4 ± 5
x = 4 + 5 or x = 4 - 5
x = 9 or x = -1
Solution Set: {9, -1}
