Write the equation of the line which passes through (2, –1) and is perpendicular to the line with equation 3y – x = 1.

You can start by swapping the x- and y-coefficients and negating one. In standard form the x-coefficient must be positive, so it is convenient to choose that.

... 3x +y = ??

The ?? is a constant chosen to make sure the line goes through the given point. If you fill in 2 for x and -1 for y, you see what the constant needs to be.

... 3x + y = 3(2) +(-1) = 5

The equation is 3x + y = 5.

a triangular prism is a 3 dimensional shape composed of triangles and rectangles. it is made from two triangular bases and three rectangular sides.