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Diketahui ac + ad + bc + bd = 32 dan c + d = 8. Tentukan nilai a + b + c + d !
Jawab :
ac + ad + bc + bd = 32
a ( c + d ) + b ( c + d ) = 32
( c + d ) ( a + b ) = 32
8 ( a + b ) = 32
( a + b ) = 4
Jadi a + b + c + d = 4 + 8 = 12