Show that the triangle with vertices's P (4; 3; 6); Q(-2; 0; 8) and R(1; 5; 0) is a right angled triangle and find its area

Question

Show that the triangle with vertices P (4; 3; 6); Q(2; 0; 8) and R(1; 5; 0) is a right angled triangle and find its area this whre im stuck:i tried to find the dot product of QP and QR i found (6,3,-2) and (3,5,-8) but their dot product is not giving me zero:

Answer 1

Hint: $$PR=\sqrt{9+4+36}=7$$ $$PQ=\sqrt{36+9+4}=7$$ $$RQ=\sqrt{1+25+64}=\sqrt{98}$$ so $$PQ^2+RQ^2=49+49=98$$