Bài 1: Tính hợp lý 4) 4. (-2 ). (-13) . (-5) . 25 6) 25.135+(-25).35; 8) 115 – 3.[48 – 64 : (25 – 17)] Bài 2: 1) x – 9 = – 25

0 bình luận về “Bài 1: Tính hợp lý 4) 4. (-2 ). (-13) . (-5) . 25 6) 25.135+(-25).35; 8) 115 – 3.[48 – 64 : (25 – 17)] Bài 2: 1) x – 9 = – 25”

1. Đáp án:

   Bài 1:

   4) 4 . (-2 ) . (-13) . (-5) . 25

   = 4 . (-5) . (-2) . 25 . (-13)

   = (-20) . (-50) . (-13)

   = 1000 . (-13)

   = -13000.

   6) 25 . 135 + (-25) . 35

   = 25 . 135 – 25 . 35

   = 25 . (135 – 35)

   = 25 . 100

   = 2500.

   8) 115 – 3 . [ 48 – 64 : (25 – 17) ]

   = 115 – 3 . [ 48 – 64 : 8 ]

   = 115 – 3 . [ 48 – 8 ]

   = 115 – 3 . 40

   = 115 – 120

   = -5.

   Bài 2:

   1) x – 9 = – 25

   x = -25 + 9

   x = -16

   3) 15 – ( 2 – 3x ) = 25

   2 – 3x = 15 – 25

   2 – 3x = -10

   -3x = -10 -2

   -3x = -12

   x = 4.

   5) |x – 5| = 5

   TH1: x – 5 = 5

   x = 5 + 5

   x = 10

   TH2: x – 5 = -5

   x = -5 + 5

   x = 0

   Trả lời

2. Bài 1:

   4) $4. (-2 ). (-13) . (-5) . 25$

   $=(4.25).[(-2).(-5)].(-13)$

   $=100.10.(-13)$

   $=1000.(-13)$

   $=-13000$

   6) $25.135+(-25).35$

   $=25.(135-35)$

   $=25.100$
   $=2500$

   8)$115 – 3.[48 – 64 : (25 – 17)]$

   $=115 – 3.[48 – 64 : 8]$

   $=115 – 3.[48 – 8]$

   $=115-3.40$

   $=115-120$

   $=-5$

   Bài 2:

   1) $x – 9 = – 25$

   $⇒x=-25+9$

   $⇒x=-16$

   Vậy $x=-16$

   2) $15- ( 2 – 3x ) = 25$

   $⇒2-3x=15-25$

   $⇒2-3x=-10$

   $⇒3x=2-(-10)$
   $⇒3x=12$
   $⇒x=4$

   Vậy $x=4$

   5) $|x-5| = 5$

   $⇒$\(\left[ \begin{array}{l}x-5=5\\x-5=-5\end{array} \right.\) 
   

   $⇒$\(\left[ \begin{array}{l}x=5+5\\x=-5+5\end{array} \right.\) 
   

   $⇒$\(\left[ \begin{array}{l}x=10\\x=0\end{array} \right.\) 
   

   Vậy $x∈{\{10,0\}}$
   

   Trả lời