(x
2
−5x+2)(x
−5x−1)=28,
x
−5x=a,
(a+2)(a−1)=28,
a
+a−30=0,
1
=−6,a
=5;
−5x+6=0,
=2,x
=3;
−5x−5=0,
D=45,
3
=
5−3
5
,x
4
5+3
.
(x
2
−5x+2)(x
2
−5x−1)=28,
x
2
−5x=a,
(a+2)(a−1)=28,
a
2
+a−30=0,
a
1
=−6,a
2
=5;
x
2
−5x+6=0,
x
1
=2,x
2
=3;
x
2
−5x−5=0,
D=45,
x
3
=
2
5−3
5
,x
4
=
2
5+3
5
.