Verified answer

f'=[(x+5)'(x-5)-(x+5)(x-5)']/(x-5)²

f'=[(1)'(x-5)-(x+5)(1)']/(x-5)²

f'=[x-5-x-5](x-5)²

f'=-10/(x-5)²

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f(x)=u/v

f'=(u'*v-u*v']/v²

f(x) = (x + 5)/(x - 5)

f(x) = g(x)/h(x)

g(x) = x + 5

g´(x) = 1

h(x) = x - 5

h´(x) = 1

regra de derivação

f´(x) = (g´(x)*h(x) - g(x)*h´(x))/h²(x)

f´(x) = (1*(x - 5) - (x + 5)*1)/(x - 5)²

f´(x) = (x - 5 - x - 5)/(x - 5)²

f´(x) = -10/(x - 5)²

pronto