The tangent vector of 1. curve x=t, Y =-T 2 and Z = T 3 at (1,-1) is (1,-2,3). What are the specific steps?

dx/dt= 1，dy/dt=-2t，dz/dt=3t？

At this time t= 1.

The tangent vector T=( 1,-2,3) is obtained by substitution.

2. The tangent vector pointing to the negative side of the X axis is (-1, 2, -3). Excuse me: Since X is negative, change the sign of X, why change the sign of all?

Because it points in the negative direction of the x axis.

therefore

X must be less than 0.

therefore

Tangent vector =-( 1,-2,3) = (-1,2,3)

All signs must be changed.