... thu VAT 10% ) l 10 x 110 x x+ = triu ng, cho loi hng th hai (k c thu VAT 8%) l 100 100 y 108 y = triu ng, cho loi hng th hai Ta 100 100 110 x 108 y + = 2.17 1.1x + 1.08 y = 2.17 100 100 y+ cú ... [0 ;10] v khong (10; + ) b) Tớnh f(8), f (10) v f(18) Gi ý a) Khi x 10 , s tin phi tr l f(x) = 6x Khi x > 10, s tin phi tr l f(x) = 6 .10 +2,5.(x -10) = 2,5x + 35 x 10 6x 2.5 x + 35 x > 10 Vy ... cam c mt trm ming, ngha l: 3x+10y =100 x + y = 17 Ta cú h phng trỡnh : x + 10 y = 100 Gii h phng trỡnh ta c: x =10; y=7 Hai s x v y tỡm c tho iu kin ca bi toỏn Vy cú 10 qu quýt v qu cam +Toỏn nng...