<PRE><B>Question 255121</B>
Solve:
25x^2 -90x = -81
;
add 81 to each side
25x^2 - 90x  + 81 = 0
:
This looks like a perfect square (25 * 81)
(5x - 9)(5x - 9) = 0
:
5x = 9
x = {{{9/5}}}
;
Check by FOILing the factors:
25x^2 - 45x - 45x + 81</PRE>