Answer:
x = ± √(39/7) + 3
Explanation:
1) divide all by 7 to get -x² + 6x - 24/7 = -(x² - 6x) - 24/7.
2) put the x, not x ², in parenthesis.
3) half the coefficient (6) of x. that is 3. Put that into same parenthesis.
4) we have -(x - 3)
5) square this and multiply out. -(x - 3) ² = -[(x - 3)² - 9)] - 24/7
= -(x - 3)² + 9 - 24/7
= -(x - 3)² + 39/7
6) -(x - 3)² + 39/7 = 0
-(x - 3)² = - 39/7
(x - 3)² = 39/7
x - 3 = ± √(39/7)
x = ± √(39/7) + 3