Bài 4: Tính hợp lí:
a) 234 x 45 + 54 x 234 + 234 b) 50 x 8 x 125 x 20
a: =234x(45+54+1)
=234x100
=23400
b: =(8x125)x(50x20)
=1000x1000
=1000000
a = 243x(45+54+1)
=243 x 100
=24300
b = (20 x 50 ) x (8x125)
=1000x1000
=1000000
a) 234 x 45 + 54 x 234 + 234
= 234 x (45+54+1) = 234 x 100 = 23400
b) 50 x 8 x 125 x 20 = (50 x 20) x (8 x 125)
= 1000 x 1000 = 1000000
Cho biểu thức: 234 x 43 + 234 x 57. Cách tính đúng là: *
A. 234 x 43 + 234 x 57 = 234 x 43 + 234 = 10 296
B. 234 x 43 + 234 x 57 = 234 x 43 + 57 = 10 119
C. 234 x 43 + 234 x 57 = 234 x (57 – 43) = 3 276
D. 234 x 43 + 234 x 57 = 234 x (43 + 57) = 23 400
Bỏ dấu ngoặc rồi tính
a) (24 - 234) + (234 - 24 - 77) b) (13 - 135 + 49) - (13+ 49)
c) 159 - 524 - (59 - 424) d) (36 + 79) + (145 - 79 - 36)
e) 334 - (117 + 234) + (42 + 117) f) 271 - [(-43) + 271 - (-17)]
a: \(\left(24-234\right)+\left(234-24-77\right)\)
\(=24-234+234-24-77\)
\(=\left(24-24\right)+\left(234-234\right)-77\)
=0+0-77
=-77
b: \(\left(13-135+49\right)-\left(13+49\right)\)
\(=13-135+49-13-49\)
\(=\left(13-13\right)+\left(49-49\right)-135\)
=0+0-135
=-135
c: \(159-524-\left(59-424\right)\)
\(=159-524-59+424\)
\(=\left(159-59\right)-\left(524-424\right)\)
=100-100
=0
d: \(\left(36+79\right)+\left(145-79-36\right)\)
\(=36+79+145-79-36\)
\(=\left(36-36\right)+\left(79-79\right)+145\)
=0+0+145
=145
e: \(334-\left(117+234\right)+\left(42+117\right)\)
\(=334-117-234+42+117\)
\(=\left(334-234\right)+\left(117-117\right)+42\)
=100+0+42
=142
f: \(271-\left[\left(-43\right)+271-\left(-17\right)\right]\)
\(=271+43-271+\left(-17\right)\)
\(=\left(271-271\right)+\left(43-17\right)\)
=0+26
=26
Tính nhanh :
a ) 43 x 27 + 93 x 43 + 57 x 61 x 59 x 57
b ) 64 x 6 + 81 x 4 + 17 x 6
43 x 27 + 93 x 43 + 57 x 61 + 59 x 57
= 43 x ( 27 + 93 ) + 57 x ( 61 + 59 )
= 43 x 120 + 57 x 120
= 120 x ( 43 + 57 )
= 120 x 100
= 1200
b) 64 x 6 + 81 x 4 + 17 x 6
= 6 x ( 64 + 17 ) + 81 x 4
= 6 x 81 + 81 x 4
= 81 x ( 6 + 4 )
= 81 x 10
= 810
A) =43 x (27+93)+57*(61+59)
=43*120+57*120
=120*(43+57)
=120*100
=12000
Bỏ dấu ngoặc rồi tính
a ) 159 − 524 − 59 − 424 ; b ) 36 + 79 + 145 − 79 − 36 ; c ) 334 − 117 + 234 + 42 + 117 ; d ) 271 − − 43 + 271 − − 17 .
a ) 159 − 524 − 59 − 424 ; = 159 − 524 − 59 + 424 = 159 − 59 − 524 − 424 = 100 − 100 = 0 b ) 36 + 79 + 145 − 79 − 36 ; = 36 + 79 + 145 − 79 − 36 = 36 − 36 + 79 − 79 + 145 = 145 c ) 334 − 117 + 234 + 42 + 117 ; = 334 − 117 − 234 + 42 + 117 = 334 − 234 − 117 − 117 + 42 = 100 + 42 = 142 d ) 271 − − 43 + 271 − − 17 . = 271 − − 43 + 271 + 17 = 271 + 43 − 271 − 17 = 271 − 271 + 43 − 17 = 26
Tìm x E Z biết
59-x/41 +57-x/43 +55-x/45 + 53-x/47 +51-x/49=-5
\(\dfrac{59-x}{41}+\dfrac{57-x}{43}+\dfrac{55-x}{45}+\dfrac{53-x}{47}+\dfrac{51-x}{49}=-5\)
\(\Leftrightarrow\dfrac{59-x}{41}+1+\dfrac{57-x}{43}+1+\dfrac{55-x}{45}+1+\dfrac{53-x}{47}+1+\dfrac{51-x}{49}+1=0\)
\(\Leftrightarrow\dfrac{100-x}{41}+\dfrac{100-x}{43}+\dfrac{100-x}{45}+\dfrac{100-x}{47}+\dfrac{100-x}{49}=0\)
\(\Leftrightarrow\left(100-x\right)\left(\dfrac{1}{41}+\dfrac{1}{43}+\dfrac{1}{45}+\dfrac{1}{47}+\dfrac{1}{49}\right)=0\)
Mà \(\dfrac{1}{41}+\dfrac{1}{43}+\dfrac{1}{45}+\dfrac{1}{47}+\dfrac{1}{49}\ne0\)
\(\Leftrightarrow100-x=0\Leftrightarrow x=100\)
Vậy x = 100
(59-x)/41+(57-x)/43+(55-x)/45=-9
Mình bạn chép đề sai, đề bài như này mới đúng nhé, bạn check lại xem đề nha :
\(\frac{59-x}{41}+\frac{57-x}{43}+\frac{55-x}{45}=-3\)
\(\Leftrightarrow\frac{59-x}{41}+1+\frac{57-x}{43}+1+\frac{55-x}{45}+1=0\)
\(\Leftrightarrow\frac{100-x}{41}+\frac{100-x}{43}+\frac{100-x}{45}=0\)
\(\Leftrightarrow\left(100-x\right)\left(\frac{1}{43}+\frac{1}{45}+\frac{1}{41}\right)=0\)
\(\Leftrightarrow100-x=0\left(\frac{1}{41}+\frac{1}{43}+\frac{1}{45}\ne0\right)\)
\(\Leftrightarrow x=100\)
Vậy : \(x=100\)
59-x/41+57-x/43+55-x/45+53-x/47+51-x/49=-5
\(\dfrac{59-x}{41}+\dfrac{57-x}{43}+\dfrac{55-x}{45}+\dfrac{53-x}{47}+\dfrac{51-x}{49}=-5\)
\(\Leftrightarrow\dfrac{59-x}{41}+1+\dfrac{57-x}{43}+1+\dfrac{55-x}{45}+1+\dfrac{53-x}{47}+1+\dfrac{51-x}{49}+1=0\)
=>100-x=0
hay x=100
