We know the formula for finding the derivative```
dy/dx = lim [f(x + δx) - f(x)]/δx
δx→0
```
If f(x) is a sum of two functions g(x) and h(x)i.e. f(x) = g(x) + h(x) then f(x + δx) = g(x + δx) + h(x + δx) Difference f(x + δx) - f(x) = g(x + δx) + h(x + δx) - (g(x) + h(x)) f(x + δx) - f(x) = g(x + δx) - g(x) + h(x + δx) - h(x) Ratio [f(x + δx) - f(x)]/δx = [g(x + δx) - g(x) + h(x + δx) - h(x)]/δx [f(x + δx) - f(x)]/δx = [g(x + δx) - g(x)]/δx + [h(x + δx) - h(x)]/δx Limit as δx→0 lim [f(x + δx) - f(x)]/δx δx→0 = lim [g(x + δx) - g(x)]/δx + lim[h(x + δx) - h(x)]/δx δx→0 δx→0 As limit of sum of two functions is equal to the sum of the limits of two functions. df/dx = dg/dx + dh/dx If f(x) is a difference of two functions g(x) and h(x) i.e. f(x) = g(x) - h(x) then df/dx = dg/dx - dh/dx df/dx = dg/dx + dh/dx if f(x) = g(x) + h(x)anddf/dx = dg/dx - dh/dx if f(x) = g(x) - h(x) |

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