1 tìm X A) 20 – 5 / ( x – 1 ) = 15 B ) 17x + x – 4x = 70 C ) 42 – ( X + 1 ) * 3 = 9 D) 70 – 35 * ( x – 3 ) = 35

0 bình luận về “1 tìm X A) 20 – 5 / ( x – 1 ) = 15 B ) 17x + x – 4x = 70 C ) 42 – ( X + 1 ) * 3 = 9 D) 70 – 35 * ( x – 3 ) = 35”

1. Đáp án:

    

   Giải thích các bước giải:

    A) `(20 – 5) / ( x – 1 ) = 15`

   `⇔ \frac{15}{x-1}=15`

   `⇔ 15(x-1)=15`

   `⇔ x-1=1`

   `⇔ x=2`

   B ) `17x + x – 4x = 70`

   `⇔ 14x=70`

   `⇔ x=5`

   C ) `42 – ( x + 1 ) × 3 = 9`

   `⇔ (x+1)×3=33`

   `⇔ x+1=11`

   `⇔ x=10`

   D) `70 – 35× ( x – 3 ) = 35`

   `⇔ 70-35x+105=35`

   `⇔ -35x=-140`

   `⇔ x=4`

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2. A) 20 – 5 : ( x – 1 ) = 15

   => 5 : ( x – 1) = 5

   => x – 1 = 1

   => x = 1

   vậy x = 1

   B ) 17x + x – 4x = 70

   => x (17 + 1 – 4 ) = 70

   => 14x = 70

   => x = 5

   Vậy x = 5

   C ) 42 – ( X + 1 ) * 3 = 9

   => ( x + 1) x 3 =   33

   => x + 1 = 11

   => x =10

   Vậy x = 10

   D) 70 – 35 * ( x – 3 ) = 35

   => 35 x (x – 3) = 35

   =>x – 3 = 1

   => x = 4

   Vậy x = 4

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