Question Number 1625 by 112358 last updated on 27/Aug/15

Answered by Rasheed Soomro last updated on 28/Aug/15
![y(x)=(1/(x−a))∫_a ^( x) ( (√(t+(√(t+(√(t+(√(t+(√(t+...)))))))))) )dt Let (√(t+(√(t+(√(t+(√(t+(√(t+...))))))))))=u Squaring both sides: t+(√(t+(√(t+(√(t+(√(t+...))))))))=u^2 t+u=u^(2 ) ⇒ u^2 −u−t=0 u=((1±(√(1+4t)))/2) y(x)=(1/(x−a)) ∫_a ^( x) (((1±(√(1+4t)))/2) )dt =(1/(2(x−a)))∫_a ^( x) (1±(√(1+4t)))dt =(1/(2(x−a)))[t±(1/6)(1+4t)^(3/2) ]_a ^x =(1/(2(x−a)))([x±((√((1+4x)^3 ))/6)]−[a±((√((1+4a)^3 ))/6)]) =(1/(2(x−a)))×((6(x−a)±(√((1+4x)^3 )) ∓(√((1+4a)^3 )) )/6) =((6(x−a)±((√((1+4x)^3 )) −(√((1+4a)^3 )) ))/(12(x−a))) y(x)=(1/2)±(((√((1+4x)^3 )) −(√((1+4a)^3 )))/(12(x−a))) y(2a)=(1/2)±(((√((1+4(2a))^3 )) −(√((1+4a)^3 )))/(12((2a)−a))) =(1/2)±(((√((1+8a)^3 )) −(√((1+4a)^3 )))/(12a))](https://www.tinkutara.com/question/Q1630.png)
Commented by 123456 last updated on 28/Aug/15
![∫_a ^x 1±(√(1+4t))dt=∫_a ^x dt±∫_a ^x (√(1+4t))dt ∫_a ^x dt=x−a ∫_a ^x (√(1+4t))dt u=1+4t⇒du=4dt t=a⇒u=1+4a t=x⇒u=1+4x ∫_a ^x (√(1+4t))dt=(1/4)∫_(1+4a) ^(1+4x) (√u)du=[((1/4)/(3/2))(√u^3 )]_(1+4a) ^(1+4x) =(((√((1+4x)^3 ))−(√((1+4a)^3 )))/6) ∫_a ^x 1±(√(1+4t))dt=x−a±(((√((1+4x)^3 ))−(√((1+4a)^3 )))/6)](https://www.tinkutara.com/question/Q1637.png)
Commented by 123456 last updated on 28/Aug/15

Commented by Rasheed Soomro last updated on 28/Aug/15

Commented by 123456 last updated on 28/Aug/15
![lim_(x→a) y(x) is like [(d/dx)∫f(x)dx]_(x=a) :) lim_(x→a) ((∫_a ^x f(x)dx)/(x−a))=lim_(x→a) ((F(x)−F(a))/(x−a))=f(a)](https://www.tinkutara.com/question/Q1647.png)
Commented by 112358 last updated on 29/Aug/15
![I created this question having the formula for the average value of a function in mind: y_(avg) =(1/(b−a))∫_a ^b f(x)dx . y_(avg) =((F(b)−F(a))/(b−a)) (∗) (∗) resembles the relation given by the mean value theorem which states that ∃c∈[a,b] such that (d/dx)f(x)∣_(x=c) =((f(a)−f(b))/(b−a)) given that f(x) is continuous ∀x∈[a,b] and differentiable ∀x∈(a,b).](https://www.tinkutara.com/question/Q1648.png)
Commented by 123456 last updated on 29/Aug/15
![or mean value theorem for integrails if f is continuous and integrable into [a,b] them ∃ξ∈[a,b] ∫_a ^b f(x)dx=f(ξ)(b−a) so for some ξ∈[a,b] y_(avg) =(1/(b−a))∫_a ^b f(x)dx=f(ξ)](https://www.tinkutara.com/question/Q1653.png)
Commented by 112358 last updated on 29/Aug/15
