line (2,3),(-1,5)
The slope between the two points is y2 -y1x2 -x1: 5 -3-1 -2
⇥ⓘ The numerator and the denominator are computed before the division: 5 -3 = 2, -1 -2 = -3
⇥ 2-3
⇥ⓘ The sign of a fraction goes in front of the bar, whether it comes from the numerator or the denominator: 2-3 = -23
⇥ -23
The line passes through the first point with this slope: y = -23·(x -2) + 3
Compute the y-intercept b = y₁ - m*x₁: 3 -(-23·2)
⇥ⓘ Two minus signs cancel out, the product of two negative numbers is positive: -(-23·2) = 23·2
⇥ 3 + 23·2
⇥ⓘ Multiplying a fraction by a number multiplies its numerator: 23·2 = 2·23 = 43
⇥ 3 + 43
⇥ⓘ To add fractions, put them over the same denominator, then add the numerators: 3 + 43 = 3·3 + 43
⇥ 3·3 + 43
⇥ⓘ Multiplications are done before additions and subtractions: 3·3 = 9
⇥ 9 + 43
⇥ⓘ The numerator and the denominator are computed before the division: 9 + 4 = 13
⇥ 133
▶Line:   y = -2x3 + 133