I think its b but im not sure
-4 is what you put on both sides Bc it’s half of b
In 8, 9, 10, all the triangles are similar, meaning corresponding sides have the same ratio.
8. hypotenuse / (short side) = 25/x = x/9
x² = 25*9 = 5²×3²
x = √(5²×3²) = 5*3 = 15
9. (long side) / (short side) = x/7 = 9/x
x² = 7*9
x = √(9*7) = 3√7
10. (short side) / (long side) = x/48 = 48/64
x = 48²/64 = 36
Answer:

Since the angle between the two vectors is not 180 or 0 degrees we can conclude that are not parallel
And the anfle is approximately 
Step-by-step explanation:
For this case first we need to calculate the dot product of the vectors, and after this if the dot product is not equal to 0 we can calculate the angle between the two vectors in order to see if there are parallel or not.
a=[1,2,-2], b=[4,0,-3,]
The dot product on this case is:

Since the dot product is not equal to zero then the two vectors are not orthogonal.
Now we can calculate the magnitude of each vector like this:


And finally we can calculate the angle between the vectors like this:

And the angle is given by:

If we replace we got:

Since the angle between the two vectors is not 180 or 0 degrees we can conclude that are not parallel
And the anfle is approximately 