Please help with this part!

I will attach a screenshot of some of what I have so far

$($b$)$ The following functions are the same mathematically, but very different in terms of their impact on the relevant MathVector. The scalar product is defined as follows.

$\backslash$lambda $($x$1,$ x$2,$ x$3,...,$ xN $)=(\backslash$lambda x$1,\backslash$lambda x$2,\backslash$lambda x$3,...,\backslash$lambda xN $)$

$$ void scaleBy$($double$)$ should change the implicit parameter by multiplying each of its values by the specified double.

$$ static MathVector multiply$($double$,$ MathVector$)$ should leave the input vector unchanged and return $($a reference to$)$ a newly created MathVector whose values are obtained by performing the relevant scalar product.