tính nhanh:
650 x 34 + 68 x 135 + 17 x 2 x 80
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650 x 34 + 34 x 2 x 135 + 34 x 80
= 650 x 34 + 34 x 270 + 34 x 80
= 34 x ( 650 + 270 + 80 )
= 34 x 1000
= 34000
Tick nha
650 x 34 + 34 x 2 x 135 + 34 x 80
= 650 x 34 + 34 x 270 + 34 x 80
= 34 x ( 650 + 270 + 80 )
= 34 x 1000
= 34000
=(2.34).135+(17.2).80+650.34
=34.(135+135+80+650)
=34.900
=30600
b) -26 - ( x - 7 ) = 0
x - 7 = -26 - 0
x - 7 = -26
x = -26 + 7
x = -19
Bài 2 :
a) 3 - ( 17 - x ) = -12
( 17 - x ) = 3 - ( -12 )
( 17 - x ) = 15
x = 17 - 15
x = 2
C1:
a) 135 x 54 + 45 x 135 + 135
= 135 x ( 54 + 45 + 1)
=135x100=13500
C2
a) 135 x 54 + 45 x 135 + 135
= 7290 + 6075 +135
= 13500
A = 78 x 31 + 78 x 24 + 78 x 17 + 22 x 72
A = 78 x ( 31 + 24 + 17 ) + 22 x 72
A = 78 x 72 + 22 x 72
A = 72 x ( 78 + 22 )
A = 72 x 100
A = 7200
C = 53 x 39 + 47 x 39 - 53 x 21 - 47 x 21
C = 39 x ( 53 + 47 ) - 21 x ( 53 - 47 )
C = 39 x 100 - 21 x 6
C = 3900 - 126
C = 3774
a. 34^2 + 66^2 + 68 x 66
= 34 x 34 + 66 x 66 + 68 x 66
= 34 x 34 + 66 x (66 + 68)
= 34 x 34 + 66 x 134
= 34 x 34 + 66 x 34 + 66 x 100
= 34 x (34 + 66) + 66 x 100
= 34 x 100 + 66 x 100
= (34 + 66) x 100
= 100 x 100
= 10000
\(34^2+66^2+68.66\)
\(=34.34+66.66+68.66\)
\(=34.34+66.\left(68+66\right)\)
\(=34.34+66.134\)
\(=34.34+66.\left(100+34\right)\)
\(=34.34+66.100+66.34\)
\(=34.\left(66+34\right)+66.100\)
\(=34.100+66.100\)
\(=\left(34+66\right).100\)
\(=100^2\)
\(=10000\)
\(A=\frac{34}{7.13}+\frac{51}{13.22}+\frac{85}{22.37}+\frac{68}{37.49}\)
\(=\frac{17.2}{7.13}+\frac{17.3}{13.22}+\frac{17.5}{22.37}+\frac{17.4}{37.49}\)
\(=17\left(\frac{2}{7.13}+\frac{3}{13.22}+\frac{5}{22.37}+\frac{4}{37.49}\right)\)
\(=\frac{17}{3}\left(\frac{6}{7.13}+\frac{9}{13.22}+\frac{15}{22.37}+\frac{12}{37.49}\right)\)
\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{13}+\frac{1}{13}-\frac{1}{22}+...+\frac{1}{37}-\frac{1}{49}\right)\)
\(=\frac{17}{3}\left(\frac{1}{7}-\frac{1}{49}\right)\)\(=\frac{17}{3}.\frac{6}{49}=\frac{17.2}{49}=\frac{34}{49}\)
Có : \(\frac{17}{24}=\frac{34}{48}\)
Vì 48 < 49 => \(\frac{34}{48}>\frac{34}{49}\). Hay \(\frac{17}{24}>A\)