Question

write a scalar equation, given it's vector equation.
[x,y,z]= [3,7,-5] + s[1,2,-1] + t[5,-2,3]

( I remember my teacher saying that you have to cross s and t, and that will be my normal and thereafter I substitue the point to find the 'D' value of the scalar equation, but when I try it, it does not give me the answer? Is my method wrong?)

Answer 1

did you get a reduced cross-product of (1,-2,-3) ?

Here is an on-line cross-product calculator:
http://www.analyzemath.com/vector_calculators/vector_cross_product.html

so your equation would be x - 2y - 3z = D
sub in your given point and you got it.