Toán Lớp 8: Giải phương trình
a, $\frac{x-85}{15}$ + $\frac{x-74}{13}$ + $\frac{x-67}{11}$+ $\frac{x-64}{9}$ = 10
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Toán Lớp 8: Giải phương trình
a, $\frac{x-85}{15}$ + $\frac{x-74}{13}$ + $\frac{x-67}{11}$+ $\frac{x-64}{9}$ = 10
Comments ( 2 )
(x-85)/15+(x-74)/13 +(x-67)/11 +(x-64)/9=10
<=>(x-85-15)/15 + (x-74-2.13)/13 + (x-67 – 3.11)/11 + (x-64-4.9)/9 =0
<=>(x-100)/15 + (x-100)/13 + (x-100)/11 + (x-100)/9=0
<=>(x-100)(1/15 +1/13+1/11+1/9)=0
Do 1/15+1/13+1/11+1/9\ne 0
<=>x-100=0
<=>x=100
Vậy S={100}
Giải đáp:
a, (x – 85)/15 + (x – 74)/13 + (x – 67)/11 + (x – 64)/9 = 10
↔ ((x – 85)/15 – 1) + ((x – 74)/13 – 2) + ((x – 67)/11 – 3) + ((x – 64)/9 – 4) = 0
↔ (x – 85 – 15)/15 + (x – 74 – 36)/13 + (x – 67 – 33)/11 + (x – 64 – 36)/9 = 0
↔ (x – 100)/15 + (x – 100)/13 + (x – 100)/11 + (x – 100)/9 = 0
↔ (x – 100).(1/15 + 1/13 + 1/11 + 1/9) = 0
↔ x – 100 = 0 (1/15 + 1/13 + 1/11 + 1/9 \ne 0)
↔ x = 100
Vậy S = {100}
$#dariana$