How do we write $y = - 3x$ in standard form?

Hint:To solve this question, first we should know the type of equation. And then we will discuss the standard form of that known equation. And then write the given equation in the standard form of their type.
Step by step solution:-
As we can see that, the given equation is in linear form.
The standard form of a Linear Equation is as:
$Ax + By = C$
Where, if at all possible, A, B and C are integers, and A is non-negative, and A,B and C have no common factors other than 1.
Now, in the given equation, we can add $3x$ to each side if the equation to transform it to standard linear form:
$y + 3x = - 3x + 3x$
Now, In R.H.S, cancel out $ - 3x$ and $3x$ :
$\therefore 3x + y = 0$ or $3x + 1y = 0$
Hence, now the given equation is in its standard form.
Note:- When an equation is given in this form, it’s pretty easy to find both intercepts (x and y). This form is also very useful when solving systems of two linear equations.