ta co vecter n(1;-2;2) la vecter phap tuyen of mp(A) vi mp(B) ll mp(A) suy ra vecter n(1;-2;2) cung la vecter phap tuyen of mp (B)
ta co I(2;-1;-2) la tam mat cau va R=4
goi A(a;b;c) la tep diem suy ra A thuoc mat cau va mp(B)
vi mp(B) tx voi mat cau suy ra vecter IA(a-2;b+1;c+2) cung phuong voi veter n(1;-2;2)
suy ra a=k+2 b=2k-1 c=2k-2
thay vao mat cau suy ra k=0 hoac k=2/3
voi k=0 ta co A(2;-1;-2) suy ra pt mp(B): (x-2)-2(y+1)+2(z+2)=0
voi k=2/3 ta coA(8/3;1/3;-2/3) suy ra pt mp(B): (x-8/3)-2(y-1/3)+2(z+2/3)=0