Root 64 is 8, if by root you mean the square root. Then the problem become -square root 84(6+8) which is the - square root of 84(14) But square root of 84 is 2(square root of 21) so the final answer comes from -2(square root 21)x14 which is -28square root (21)
That doesn't factor neatly. Applying the quadratic formula, we find two imaginary solutions: -8 plus or minus i times the square root of 11. x = -8 + 3.3166247903554i x = -8 - 3.3166247903554i where i is the imaginary square root of -1
The principle square root of 64 is ±8. 8. * * * * * The square roots of 64 are +8 and -8. The PRINCIPAL square root is the positive root, +8. So, the answer to the question that was asked is +8 not ±8.