Question

Malcolm says that y = -1.5x + 4 in standard form is 1.5x + y = 4. What is the error that Malcolm made?

Answer 1

Recall that the standard form of the line is of the form

`Ax+By=C`

where A,B and C are constants. What is most important is that in standard form, the numbers A,B,C are integers. This means that they cannot be fractions nor decimal numbers.

Starting from the equation y=-1.5x+4, Malcolm did right by adding 1.5x on both sides

so we have 1.5x+y=4. However, 1.5 is a decimal number. So he needs to multiply the whole equation by 2, so he does not have any more decimals on the standard form. That is

`2\cdot(1.5x+y)=4\cdot2`

so the standard form is

`3x+2y=8`