Toán học 20 Tháng Hai, 2023 No Comments By Diệu Hằng Toán Lớp 7: Tìm x A) 1500.(x-7)=3 B) 128-3.(x+4=23 C) [(14.x+26).3+55]:5=35 D) 720:[41-(2x-5)]:2mũ3=2mũ.5
a) 1500.(x-7)=3 =>x-7=3:1500 =>x-7=1/500 =>x=1/500+7 =>x=7,002 b) 128-3(x+4)=23 =>3(x+4)=128-23 =>3(x+4)=105 =>x+4=105:3 =>x+4=35 =>x=35-4 =>x=31 c) [(14x+26).3+55]:5=35 =>(14x+26).3+55=35×5 =>(14x+26).3+55=175 =>(14x+26).3=175-55 =>(14x+26).3=120 =>14x+26=120:3 =>14x+26=40 =>14x=40-26 =>14x=14 =>x=14:14 =>x=1 d) 720:[41-(2x-5)]:2^3=2^5 =>720:[41-(2x-5)]:8=32 =>90:[41-(2x-5)]=32 =>41-(2x-5)=90:32 =>41-(2x-5)=2,8125 =>2x-5=41-2,8125 =>2x-5=38,1875 =>2x=38,1875+5 =>2x=43,1875 =>x=43,1875:2 =>x=21,59375 Trả lời
a) 1500 . ( x – 7) = 3 ( x – 7) = 3 : 1500 x – 7 = 0,002 x = 0,002 + 7 x = 7,002 b) 128 – 3 ( x +4 ) = 23 3 ( x + 4) = 128 – 23 3 ( x + 4) = 105 ( x + 4) = 105 : 3 x + 4 =35 x = 35 – 4 x = 31 c) [(14. x + 26) . 3 + 55] : 5 = 35 [(14. x + 26) . 3 + 55] = 35 . 5 (14. x + 26) . 3 + 55 =175 ( 14 . x + 26). 3 = 175 – 55 ( 14 . x + 26). 3 = 120 ( 14 . x + 26) = 120 : 3 14 . x + 26 = 40 14 . x = 40- 26 14 . x =14 x = 14 : 14 x = 1 d)720 : [ 41 – ( 2x – 5)] : 2³ = 2^5 720 : [ 41 – ( 2x – 5)] : 8 = 32 720 : 8 :[ 41 – ( 2x – 5)] = 32 90 : [ 41 – ( 2x – 5)] = 32 [ 41 – ( 2x – 5)] = 90 : 32 41 – ( 2x – 5) = 2,8125 ( 2x – 5) = 41 – 2,8125 ( 2x – 5) =38,1875 2x = 38,1875 + 5 2x = 43,1875 x =21,59375 Trả lời
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