derivative of (4-2x-x^2/(x^2-6))
1) Let's perform the differentiation: ddx(4 -2x -x2x2 -6)
ⓘ The derivative of a sum is the sum of the derivatives: ddx(4 -2x -x2x2 -6) = 0 + ddx(-2x) + ddx(-x2x2 -6)
0 + ddx(-2x) + ddx(-x2x2 -6)
We differentiate p1 = x2 and q2 = x2 -6 using: ddx(p1q2) = ddx(p1)·q2 -p1·ddx(q2)q22
2) Let's differentiate p1: ddx(x2)
ⓘ The derivative of x^n is n*x^(n-1): ddx(x2) = 2x
2x
3) Let's differentiate q2: ddx(x2 -6)
ⓘ The derivative of a sum is the sum of the derivatives: ddx(x2 -6) = ddx(x2) + 0
ddx(x2) + 0
ⓘ Adding 0 changes nothing: ddx(x2) + 0 = ddx(x2)■The derivative of x^n is n*x^(n-1): ddx(x2) = 2x
2x
4) Let's evaluate the resulting derivative (p1q2)': -2x·(x2 -6) -x2·2x(x2 -6)2
ⓘ Multiplying powers with the same base adds the exponents: x2x = x3
-2x·(x2 -6) -2x3(x2 -6)2
ⓘ The minus sign of the fraction goes into the numerator or the denominator, changing the sign of each of its terms: -2x·(x2 -6) -2x3(x2 -6)2 = -2x·(x2 -6) + 2x3(x2 -6)2
-2x·(x2 -6) + 2x3(x2 -6)2
ⓘ What the terms have in common is factored out, so that the fraction can be simplified: -2x·(x2 -6) + 2x3(x2 -6)2 = 2x·(-(x2 -6) + x2)(x2 -6)2
2x·(-(x2 -6) + x2)(x2 -6)2
ⓘ A minus sign before a parenthesis changes the sign of each of its terms: -(x2 -6) = -x2 + 6
2x·(-x2 + 6 + x2)(x2 -6)2
ⓘ Like terms are grouped by adding their coefficients: -x2 + x2 = 0
2x·(0 + 6)(x2 -6)2
ⓘ Adding 0 changes nothing: 0 + 6 = 6
ⅰ 2·6 = 12
12x(x2 -6)2
5) Then you can resume the derivation:
ⅰ ddx(-x2x2 -6) = 12x(x2 -6)2
-2 + 12x(x2 -6)2
▶Derivative:   12x(x2 -6)2 -2