Passage of a norm of a vector exercise
I've an example of vector exercise that achieved the following step onwards to resolving. |vector r| is the norm of the vector.
|vector r|^2 = 100(25t^2-14t+2) = 100((5t-(14/10)^2) - (14/10)^2 +2)
I don't understand how the passage is made, because for me the values inside the parameter of the first count is a quadratic function who has the consequent result:
Can anybody explain me how the passage of the |vector r|^2 is made?