2x2 - x = 21
Subtract 21 from each side . . 2x2 - x - 21 = 0
Factor the left side . . . . . . . . (2x - 7) ( x + 3) = 0
If (2x - 7 = 0), then . . . . . x = 3.5
If (x + 3 = 0), then . . . . . x = - 3
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(x - 7)(x - 3)
21 and 84
21 is the largest factor of 21
The greatest factor of 21 and 16 is 21, which is a factor of 21 but not of 16.
The greatest common factor of 21 and 63 is 21.Since 21 is a factor of 63, it is automatically the GCF.