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Question -

Let f = {(1, тИТ1), (4, тИТ2), (9, тИТ3), (16, 4)} and g = {(тИТ1, тИТ2), (тИТ2, тИТ4), (тИТ3, тИТ6), (4, 8)}. Show that gof is defined while fog is not defined. Also, find gof.



Answer -

Given f┬а= {(1,тИТ1), (4, тИТ2), (9, тИТ3), (16, 4)} and┬аg┬а= {(тИТ1, тИТ2), (тИТ2, тИТ4), (тИТ3, тИТ6),(4, 8)}

f: {1, 4, 9, 16} тЖТ {-1, -2, -3, 4} and┬аg: {-1, -2, -3, 4} тЖТ {-2, -4, -6,8}

Co-domainof┬аf┬а= domain of┬аg

So,┬аgof┬аexists and┬аgof: {1, 4, 9, 16} тЖТ {-2, -4, -6, 8}

(gof)┬а(1)┬а=┬аg┬а(f┬а(1))┬а=┬аg┬а(тИТ1)┬а=┬атИТ2

(gof)┬а(4)┬а=┬аg┬а(f┬а(4))= g┬а(тИТ2)┬а=┬атИТ4

(gof)┬а(9)┬а=┬аg┬а(f┬а(9))┬а=┬аg┬а(тИТ3)┬а=┬атИТ6

(gof)┬а(16)┬а=g┬а(f┬а(16))┬а= g┬а(4)┬а=┬а8

So,┬аgof┬а=┬а{(1,┬атИТ2),┬а(4,┬атИТ4),┬а(9,┬атИТ6),┬а(16,┬а8)}

But the co-domainof┬аg┬аis not same as the domain of┬аf.

So,┬аfog┬аdoes not exist.

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