Răspuns:
1, 3, 5, 7
Explicație pas cu pas:
a,b,c,d sunt in progresie aritmetica => b=a+r, c=a+2r, d=a+3r unde r-ratia
A×B=[tex]\left[\begin{array}{ccc}1&1\\-1&1\\\end{array}\right] [/tex]×[tex]\left[\begin{array}{ccc}a&b\\c&d\end{array}\right] [/tex]=[tex]\left[\begin{array}{ccc}a+c&b+d\\-a+c&-b+d\end{array}\right] [/tex]=[tex]\left[\begin{array}{ccc}2b&2c\\d-3&c-1\end{array}\right] [/tex]=C
⇒ a+c=2b b+d=2c -a+c=d-3 -b+d=c-1
⇒
-b+d=c-1 ⇒ -(a+r)+(a+3r)=(a+2r)-1 ⇒ a=1
-a+c=d-3 ⇒ -a+(a+2r)=(a+3r)-3 ⇒ r=3-a=2
b=a+r=1+2=3, c=a+2r=1+2·2=5, d=a+3r=1+3·2=7
