10.02.2015 Views

MCS 351 ENGINEERING MATHEMATICS SOLUTION OF ...

MCS 351 ENGINEERING MATHEMATICS SOLUTION OF ...

MCS 351 ENGINEERING MATHEMATICS SOLUTION OF ...

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

∞∑<br />

4. Let<br />

n=0<br />

n n<br />

n! (z + 2i)n . First of all, center is −2i since<br />

Let z n = nn<br />

n! (z + 2i)n .As<br />

lim<br />

n→∞<br />

∣<br />

n n<br />

n!<br />

(n+1) ( n+1)<br />

(n+1)!<br />

radius of convergence is 1 e .<br />

| = lim<br />

n→∞<br />

z + 2i = 0 ⇒ z = −2i.<br />

n n (n + 1)<br />

= lim<br />

(n + 1) n+1 n→∞<br />

n n<br />

(n + 1) n = lim<br />

( n ) n 1 =<br />

n→∞ n + 1 e ,<br />

5. Let<br />

∞∑<br />

n=0<br />

n!<br />

n n (z + 1)n . The center point is −1 since<br />

Let z n = n!<br />

n n (z + 1) n . Then<br />

lim<br />

n→∞<br />

we say that radius of convergence is e.<br />

∣<br />

z + 1 = 0 ⇒ z = −1.<br />

n!<br />

n n<br />

(n+1)!<br />

(n+1) ( n+1)<br />

| = lim<br />

n→∞<br />

(n + 1) n = e,<br />

n<br />

15.3<br />

1-3 Radius of convergence by differentiation or integration :<br />

1. Let<br />

∞∑<br />

n=2<br />

n(n − 1)<br />

3 n (z − 2i) n . Since<br />

lim<br />

n→∞<br />

we say that radius of convergence is 1 4 .<br />

∣<br />

4 n<br />

n(n+1)<br />

4 n+1<br />

(n+1)(n+2)<br />

n + 2<br />

| = lim<br />

n→∞ 4n = 1 4 ,<br />

2. Let<br />

∞∑<br />

n=1<br />

4 n<br />

n(n + 1) zn . Because<br />

radius of convergence is found that 3.<br />

3. Let<br />

∞∑<br />

n=1<br />

lim ∣ n(n−1)<br />

3 n<br />

n→∞<br />

| = lim<br />

n(n+1) n→∞<br />

3 n+1<br />

3n − 3<br />

n + 1 = 3,<br />

n<br />

2 n (z + i)2n . Radius of convergence for this serie is 2 in that<br />

lim<br />

n→∞<br />

∣<br />

n<br />

2 n<br />

n+1<br />

n→∞<br />

2 n+1 | = lim<br />

47<br />

2n<br />

n + 1 = 2.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!