λa stretches a by a factor of λ; if λ is negative the arrow flips around, and its length becomes |λ||a|.
Module goal. Define the three linear operations, addition, subtraction, and scalar multiplication, by drawing arrows, and learn the rules that govern them.
eastmath.com · 27.2 Adding, Subtracting, and Scaling Vectors · 27.2.4 Scaling a Vector