A³-5a²+20-4a=0. Решите пожалуиста

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(a³-5a²) +4(5 -a) =0 a²(a -5) -4(a -5) =0 (a -5)(a² -4) =0 a -5 =0, a =5 a² -4 =0, (a -2)(a +2) =0 a -2 =0, a =2 a +2 =0, a= -2 ответ: a= -2, a =2, a =5