(5-a)^2-(a-3)^2 при а=-1/4

Question

(5-a)^2-(a-3)^2 при а=-1/4

Answer 1

( 5 - а )^2 - ( а - 3 )^2 = 25 - 10а + а^2 - а^2 + 6а - 9 = - 4а + 16
а = - 1/4
- 4 • ( - 1/4 ) + 16 = 1 + 16 = 17
Ответ 17

Answer 2

A² -b² =(a -b)(a +b)

(5 -a)² -(a -3)² =(5-a -(a-3))(5-a +(a-3)) =(5-a -a+3)(5-a +a-3) =(8 -2a)*2 =16 -4a =16 -4*(-1/4) =16 +4/4 =16 +1 =17