derivative of (7x^2/(x^3))
1) Let's perform the differentiation: ddx(7x2x3)
ⓘ The original denominator must remain nonzero. The fraction is simplified by dividing the numerator and the denominator by their common factor: 7x2x3 = 7x
ddx(7x)
We differentiate p1 = 7 and q2 = x using: ddx(p1q2) = ddx(p1)·q2 -p1·ddx(q2)q22
2) Let's perform the differentiation p1: ddx(7)
ⓘ The derivative of a constant is zero: ddx(7) = 0
0
3) Let's perform the differentiation q2: ddx(x)
ⓘ The derivative of x is 1: ddx(x) = 1
1
4) Let's evaluate the resulting derivative (p1q2)': 0·x -7·1x2
ⓘ A product with a zero factor is zero: 0·x = 0
0 -7x2
ⓘ Adding 0 changes nothing: 0 -7 = -7
-7x2
5) You can then resume the derivation:
ⅰ ddx(7x) = -7x2
▶Derivative:   -7x2