Answer: 2x+3y+4z = 12
Other answers are possible.
=====================================================
Step-by-step explanation:
The normal vector is n = (a,b,c) = (2,3,4)
The point on the plane is (p,q,r) = (2,4,-1)
Plug those values into the template below and simplify
a(x-p) + b(y-q) + c(z-r) = 0
2(x-2) + 3(y-4) + 4(z-(-1)) = 0
2(x-2) + 3(y-4) + 4(z+1) = 0
2x-4 + 3y-12 + 4z+4 = 0
2x+3y+4z-12 = 0
2x+3y+4z = 12
This is one way to express the cartesian form of the equation.