Solución

a. r=3,5,9+t7,12,7,tR \bold{r}=\lang −3,5,9\rang+t\lang 7,−12,−7\rang, t\isin\Reals
b. x=3+7t,y=512t,z=97t,tRx=−3+7t,y=5−12t,z=9−7t, t\isin\Reals
c. x+37=y512=z97\frac{x+3}{7}=\frac{y−5}{−12}=\frac{z−9}{−7}
d. x=3+7t,y=512t,z=97t,t[0,1]x=−3+7t,y=5−12t,z=9−7t, t\isin[0,1]