The sum of 2 numbers is 20. If we add to each number its square root, the product of both sums is 155.55. Find the two numbers with ǫ = 10−4

see in given solution

Step-by-step explanation:

The two numbers are a = 13. 5 and b = 6.51

Step-by-step explanation:

Data:

Let the two numbers be a and b respectively.

sum of two numbers is 20, so a + b = 20                    ...1

sum plus square roots multiplied gives 155.55 so (a+√a) (b+√b) = 155.55  ...2

let f(y) = [20-b+√(20-b)]×[(b+√b)]-155.55 = 0

Multiplying out the terms gives;

f(y) = 20y-b²+20√b - b√b+b√(20-b)+√b·√(20-b) - 155.55 = 0

differentiating:

f'(y) =

applying the Newton-Ralphson iteration method with the initial estimate of real zero roots gives P₀ = 10

That is

letting  P₀ = 10 and iterating, the convergence occurs for b to 4 decimal places at P₇ = 6.51 = b

we also obtain from equation (1)

a + b = 20

a       = 20 - b

      a = 20 - 6.51

       a = 13.5

Two numbers therefore are a= 13.5 and b = 6.51

answer: c

substitute in the values.

for a:

f(0) = 0 + 9

f(0) = 9

a is a solution.

for b:

f(7) = 14 + 9

f(7) = 23

b is a solution.

for c:

f (3) = 6 + 9

f(3) = 15

c is not a solution. it's supposed to be 14.

for d:

f(2) = 4 + 9

f(2)= 13

d is a solution.