Răspuns:
Explicație pas cu pas:
3.C.E x apartine R
3|x|-4x+25=5
3|x|-4x=20
3x-4x=20.....-x=20.......x=-20
-3x-4x=20.....-7x=20.....x=-20/7
4.C.E..delta<0...x apartine R
ridicam la patrat
x^2-6x+21=16
x^2-6x+5=0
x1,2= (6+-radical(36-20))/2
x1= (6-4)/2= 1
x2=(6+4)/2=5