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Question Number 1566 by 112358 last updated on 20/Aug/15

H o w d o e s o n e u s e t h e f o l l o w i n g

n o t a t i o n ? {I t}^{'} s n e w t o m y

u n d e r s t a n d i n g o f u s i n g o n l y

o n e s i g m a s i g n .

F o r e . g \underset{j = 1}{\sum^{m}} \underset{i = 1}{\sum^{n}} (i + 1) (j - 1)

Commented by Rasheed Soomro last updated on 20/Aug/15

C o n s i d e r i t a s

\underset{j = 1}{\sum^{m}} (\underset{i = 1}{\sum^{n}} (i + 1) (j - 1))

Commented by 112358 last updated on 20/Aug/15

S o f o r e . g

\underset{j = 1}{\sum^{3}} (\underset{i = 1}{\sum^{4}} (i + 1) (j - 1)) = \underset{j = 1}{\sum^{3}} {(j - 1) [2 + 3 + 4 + 5]}

= \underset{j = 1}{\sum^{3}} {14 (j - 1)}

= 14 \times 0 + 14 \times 1 + 14 \times 2

= 42 ?

Commented by Rasheed Soomro last updated on 20/Aug/15

I t h i n k s o .

A l t e r n a t e w a y (f o r t e s t i n g y o u r a n s w e r)

i = 1, 2, 3, 4; f o r e a c h i, j = 1, 2, 3

L e t A_{i} = {1, 2, 3, 4} a n d A_{j} = {1, 2, 3}

E v a l u a t e t h e e x p r e s s i o n [(i + 1) (j - 1)] f o r e v e r y p a i r (i, j) o f A_{i} \times A_{j}

a n d t h e n a d d .