Question

Used use euler's method with step size 0.1 to estimate y(0.5), where y(x) is the solution of the initial-value problem y ' = y + 4xy, y(0) = 1. (round the answer to four decimal places.)

Answer 1

We want to solve the Initial Value Problem y' = y + 4xy, with y(0) = 1.

To use Euler's method, define
y(i+1) = y(i) + hy'(i),  for i=0,1,2, ..., 
where
h = 0.1, the step size.,
x(i) = i*h

1st step.
y(0) = 1 (given) and x(0) = 0.
y(1) ≡ y(0.1) = y(0) + h*[4*x(0)*y(0)] = 1 

2nd step.
x(1) = 0.1
y(2) ≡ y(0.2) = y(1) + h*[4*x(1)*y(1)] = 1 + 0.1*(4*0.1*1) = 1.04

3rd step.
x(2) = 0.2
y(3) ≡ y(0.3) = y(2) + h*[4*x(2)*y(2)] = 1.04 + 0.1*(4*0.2*1.04) = 1.1232

4th step.
x(3) = 0.3
y(4) ≡ y(0.4) = y(3) + h*[4*x(3)*y(3)] = 1.1232 + 0.1*(4*0.3*1.1232) = 1.258

5th step.
x(4) = 0.4
y(5) ≡ y(0.5) = y(4) + h*[4*x(4)*y(4)] = 1.258 + 0.1*(4*0.4*1.258) = 1.4593

Answer:  y(0.5) = 1.4593