Răspuns:
a) = 5100 ; b) = 4095
Explicație pas cu pas:
a) x + y = 75 ; z + t = 68
xz + xt + yz + yt = ?
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xz + xt + yz + yt = x·(z+t) + y·(z+t) = (z+t)·(x+y) =
= 68·75 = 5100
b) x + z = 45 ; y+t=91
xy + xt + yz + zt = ?
----------------------
xy + xt + yz + zt = x·(y+t) + z(y+t) = (y+t)·(x+z) =
= 91·45 = 4095
