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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: Bài 19: Tìm x tự nhiên, biết: a) 15 : (x+2) = ( $3^{3}$ + 3) : 10 b) 70 : ( x – 3) = ($3^{4}$ -1 ) : 4 – 10 c) 240 : (x – 5) = $2^{2}$

Toán Lớp 6: Bài 19: Tìm x tự nhiên, biết:
a) 15 : (x+2) = ( $3^{3}$ + 3) : 10
b) 70 : ( x – 3) = ($3^{4}$ -1 ) : 4 – 10
c) 240 : (x – 5) = $2^{2}$ . $5^{2}$ – 20
d) 320 : (x-1) = ($5^{3}$ – $5^{2}$) : 4 + 15

Comments ( 2 )

  1. a)15:(x+2)=(3^3+3):10
    ⇔15×10=(x+2)(3^3+3)
    ⇔150=27x+3x+54+6
    ⇔90=30x
    ⇔x=3
    b)70:(x-3)=(3^4-1):4-10
    ⇔70:(x-3)=(81-1)/4-10
    ⇔70:(x-3)=80/4-10
    ⇔70:(x-3)=10
    ⇔70:10=x-3
    ⇔x-3=7
    ⇔x=4
    c)240:(x-5)=2².5²-20
    ⇔240:(x-5)=4.25-20
    ⇔240:(x-5)=100-20
    ⇔(x-5)=240:80
    ⇔x-5=3
    ⇔x=8
    d)320:(x-1)=(5^3-5^2):4+15
    ⇔320:(x-1)=(125-25):4+15
    ⇔320:(x-1)=25+15
    ⇔x-1=320:40
    ⇔x-1=8
    ⇔x=9

  2. Lời giải và giải thích chi tiết:
     a) 
    15:(x+2) =(3^3+3) :10
    15: (x+2)= (27+3):10
    15 : (x+2) =30:10
    15 : (x+2)= 3 
    x+2 = 5 
    x= 5-2= 3 
    b) 
    70:(x-3)=(3^4 -1):4-10
    70:(x-3) = (81-1):4 -10
    70: (x-3)= 80: 4-10
    70:(x-3)= 20-10
    70:(x-3) = 10 
    x-3= 70:10
    x-3 = 7 
    x= 7+3 = 10
    c) 240:(x-5)= 2^2 .5^2-20
    240 : (x-5) = 4.25-20
    240:(x-5)=100-20
    240 :(x-5) = 80 
    x-5 = 240 : 80 = 3
    x= 5+3=8
    d) 
    320: (x-1) = ( 5^3-5^2) :4 +15 
    320 : (x-1)=(125-25):4+15
    320:(x-1) = 100:4+15
    320:(x-1)= 25+15
    320: ( x-1)= 40
    x-1 = 320:40= 8
    x= 8+1 =9

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222-9+11+12:2*14+14 = ? ( )

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