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Integrals

Question
CBSEENMA12032592

Show that:
integral subscript 1 superscript 5 open vertical bar straight x minus 3 close vertical bar space dx space equals space 4

Solution

Let I = integral subscript 1 superscript 5 open vertical bar straight x minus 3 close vertical bar space dx
For        1 less or equal than straight x less or equal than 3 comma space space straight x minus 3 space less or equal than space 0 space space space space space space space space rightwards double arrow space space space space open vertical bar straight x minus 3 close vertical bar space equals space minus left parenthesis straight x minus 3 right parenthesis
and for 3 less or equal than straight x less or equal than 5 comma space space space straight x minus 3 greater or equal than 0 space space space space space rightwards double arrow space space space open vertical bar straight x minus 3 close vertical bar space equals space straight x minus 3
therefore space space space space straight I space equals space integral subscript 1 superscript 3 open vertical bar straight x minus 3 close vertical bar dx space space plus integral subscript 3 superscript 5 open vertical bar straight x minus 3 close vertical bar space dx space equals space minus integral subscript 1 superscript 3 left parenthesis straight x minus 3 right parenthesis dx space plus integral subscript 3 superscript 5 left parenthesis straight x minus 3 right parenthesis space dx
            equals negative open square brackets straight x squared over 2 minus 3 straight x close square brackets subscript 1 superscript 3 space plus space open square brackets straight x squared over 2 minus 3 straight x close square brackets subscript 3 superscript 5
equals space minus open square brackets open parentheses 9 over 2 minus 9 close parentheses space minus open parentheses 1 half minus 3 close parentheses close square brackets plus open square brackets open parentheses 25 over 2 minus 15 close parentheses minus open parentheses 9 over 2 minus 9 close parentheses close square brackets space equals space 9 over 2 minus 5 over 2 minus 5 over 2 plus 9 over 2 equals 4.

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