Answer:
Step-by-step explanation:
-a^2 = 81-18a
a^2 - 18a + 81 = 0
a^2 - 9a - 9a + 81 = 0
(a^2 - 9a) - (9a - 81) = 0
a(a - 9) - 9(a - 9) = 0
(a - 9)(a - 9) = 0
a - 9 = 0 or a - 9 = 0
a = 9 or a = 9
a= 9
-a^2 = 81 - 18a = 0
Rearranging the equation becomes:
a^2 -18a + 81 = 0
Solving the quadratic equation :
a^2 -9a - 9a + 81 = 0
a (a - 9) - 9 (a - 9)=0
(a - 9)(a-9) = 0
Theresfore,
a = +9
