Câu 1:

`a)` `vec(u_(Delta))=(3; -2;1)`

`=>` $\fbox{Sai}$

`b)` $\fbox{Đúng}$

`c)`

Vì `d////Delta=> vec(u_d)=vec(u_(Delta))=(3;-2;1)`

`=>` `d: (x-3)/3=(y-1)/(-2)=(z-2)/1`

`=>` $\fbox{Sai}$

`d)` 

Ta có: `{(vec(u_(Delta))=(3;-2;1)),(vec(u_(Delta^'))=(5;-1;2)):}`

`=>` `[vec(u_(Delta)),vec(u_(Delta^'))]=(-3;-1;7) ne vec(0)`

Ta có: `{(M_1 in Delta=>M_1(0;1;4)),(M_2 in Delta^'=> M_2(3; -1; 5)):}`

`=>` `vec(M_1M_2)=(3; -2;1)`

`=>` `[vec(u_(Delta)),vec(u_(Delta^'))]* vec(M_1M_2)=-3*3-1*(-2)+7*1=0`

`=>` Đường thẳng `Delta` và đường thẳng `Delta^'` cắt nhau

`=>` $\fbox{Đúng}$

Câu 2:

`a)`

Tâm `I(2;-1;1)=>` Bán kính `R=sqrt(2^2+1^2+1^2-(-19))=5`

`=>` $\fbox{Sai}$

`b)` `d(I, Oz)=(|0*3+0*(-1)+1*1|)/(sqrt(0^2+0^2+1^2))=1`

`=>` $\fbox{Sai}$

`c)` Xét: `IA=sqrt((2-2)^2+(1+1)^2+(4-1)^2)=sqrt13 <R`

`=>` Điểm `A` nằm trong mặt cầu 

`=>` $\fbox{Sai}$

`d)`

Ta có: `{(vec(n_(P))=(2;2;-1)),(vec(n_(Oxy))=(1;0;0)):}`

`=>` `cos((P),(Oxy))=(|2*1+2*0-1*0|)/(sqrt(2^2+2^2+1^2)*sqrt(1^2+0^2+0^2))=2/3`

`=>` `((P)","\ (Oxy))~~48,4^@< 72^@`

`=>` $\fbox{Sai}$