質問: Giúp em nhanh ạ a)x+200=1+3+5+7+.....+313 b)x+2500=2+4+6+....+320 c)x+10(mũ10)=9+99+999+.....+9999999999
回答: **a)x+200=1+3+5+7+.....+313** x+200=(313-1) ÷ 2+1 x+200=(313+1) × 157 ÷ 2 x+200=24649 x=24649-200 x=24449 **b)x+2500=2+4+6+....+320** x+2500=(320-2) ÷ 2+1 x+2500=(320+2) × 110 ÷ 2 x+2500=17710 x=15210 **c)$(x+10)^{10}$ =9+99+999+.....+9999999999** $(x+10)^{10}$ =(10-1)($10^{2}$ -1)...($10^{10}$ )