Question

why linear equation forms straight line

Answer 1

First and foremost, a linear equation is a direct relationship between two variables. If I have an amount of thing one, I always have 1/2 that amount of thing two. This is the same as saying y=(1/2)x. Every linear equation is just some complex way of writing the above. However you can add a “c” at the end to change its y intercept or make the coefficient of x steeper or shallower. This is called slope. When you take calculus slope becomes extremely important. Regardless, the reason why linear functions always result in straight lines is because they simply are relating two variables in a proportionate manner.