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a. ( 123 + 39 ) -23
= 123 + 39 - 23
= ( 123 - 23 ) + 39
= 100 + 39
= 139
b. 64 . 32 + 32 . 36
= 32 . ( 64 + 36 )
= 32 . 100
= 3200
c. 62 .4 + 2.52 -10
= 36 . 4 + 2 . 25 -10
= 114 + 50 - 10
= 114 + 40
= 151
d.( 5 . 23 - 2 . 3 2 ) : 11 +5 - I-5I
= ( 5 . 8 - 2 . 9 ) : 11 + 5 - 5
= ( 40 -18 ) : 11 + 0
= 22 : 11 + 0
= 2 + 0
= 2
1 Tính nhanh
a) \(-14+12+\left(-12\right)\left(2^3-7\right)\)
\(=-14+\left[12+\left(-12\right)\right].1\)
\(=-14+0.1\)
\(=-14+0=-14\)
b) \(\left(-5\right)+2\left(-15\right)-\left(-3\right)+\left|-10\right|\)
\(=\left(-5\right)+\left(-30\right)-\left(-3\right)+10\)
\(=\left(-35\right)-\left(-3\right)+10\)
\(=\left(-32\right)+10\)
\(=-22\)
c) \(68.\left(12+32\right)-32.\left(68-12\right)\)
\(=68.44-32.56\)
\(=2992-1792\)
\(=1200\)
d) \(89-\left(-43\right)-32\)
\(=132-32\)
\(=100\)
e) \(-12.\left(-6\right)^2+\left(-4\right)^3.12\)
\(=-12.36+64.12\)
\(=\left(-12+12\right).\left(36+64\right)\)
\(=0+100\)
\(=100\)
a)(x-6)2 . (x-6) =64
(x-6)3=64
(x-6)3=43
=>x-6=3
x=9
b)(x+5)3 : (x+5) =144
(x+5)2=144
(x+5)2=122
=>x+5\(\in\left\{12;-12\right\}\)
\(\Rightarrow x\in\left\{7;-17\right\}\)
c)3x+42=196 : (194 . 19)-2.12036
3x+42=196 :195-2
3x+42=19-2
3x+42=17
3x+16=17
3x=1
=>x=0
d)(19x + 2.52) =52 - 42
(19x + 2.52) =25-16
(19x + 2.52) =9
19x + 50 =9
19x = -41
x=\(\frac{-41}{19}\)
tính hợp lí(nếu có thể)
(52004 - 52006):(52005.5)
=(52004 - 52006):52006
=(52004 - 52006).\(\frac{1}{5^{2006}}\)
=\(\frac{5^{2004}}{5^{2006}}\) - 1
=\(\frac{1}{5^2}\) -1
=\(\frac{1}{25}-1=\frac{-24}{25}\)
1)
33 . 18 + 72 . 42 - 41 . 18
= 33 . 18 + 18 . 43 - 41 . 18
= 18 . ( 33 + 43 - 41 )
= 18 . 50
= 900
2) ( 56 . 46 - 25 . 23 ) : 23
= ( 112 . 23 - 25 . 23 ) : 23
= ( 112 - 25 ) . 23 : 23
= 87 . 23 : 23
= 87
3) ( 76 . 34 - 19 . 64 ) : ( 38 . 9 )
= ( 19 . 136 - 19 . 64 ) : ( 19 . 18 )
= 19 . ( 136 - 64 ) : ( 19 . 18 )
= 19 . 72 : 19 . 18
= 19 . 4
= 76
4) ( 5 . 411 - 3 . 165 ) : 410
= ( 5 . 411 - 3 . 410 ) : 410
= ( 20 . 410 - 3 . 410 ) : 410
= ( 20 - 3 ) . 410 : 410
= 17
1)\(79-5\left(11-x\right)=34\)
\(\Rightarrow79-55+5x=34\)
\(\Rightarrow24+5x=34\)
\(\Rightarrow5x=-10\)
\(\Rightarrow x=-2\)
Vậy \(x=-2\)
2)\(32+2\left(7-x\right)=40\)
\(\Rightarrow32+14-2x=40\)
\(\Rightarrow46-2x=40\)
\(\Rightarrow2x=6\)
\(\Rightarrow x=3\)
Vậy \(x=3\)
3)\(\left(166-2x\right).8^9=2.8^{11}\)
\(\Rightarrow\left(83-x\right).2.8^9=2.8^{11}\)
\(\Rightarrow83-x=8^3\)
\(\Rightarrow83-x=512\)
\(\Rightarrow x=-429\)
Vậy \(x=-429\)
4)\(5^2.x-2^3.x=51\)
\(\Rightarrow x\left(5^2-2^3\right)=51\)
\(\Rightarrow x\left(25-8\right)=51\)
\(\Rightarrow17x=51\)
\(\Rightarrow x=3\)
Vậy \(x=3\)
5)\(3^x+4.3^x=5.3^7\)
\(\Rightarrow3^x\left(1+4\right)=5.3^7\)
\(\Rightarrow5.3^x=5.3^7\)
\(\Rightarrow3^x=3^7\)
\(\Rightarrow x=7\)
Vậy \(x=7\)
6)\(7.2^x-2^x=6.32\)
\(\Rightarrow2^x\left(7-1\right)=6.2^5\)
\(\Rightarrow6.2^x=6.2^5\)
\(\Rightarrow2^x=2^5\)
\(\Rightarrow x=5\)
Vậy \(x=5\)
7)\(15^{3-x}=225\)
\(\Rightarrow15^{3-x}=15^2\)
\(\Rightarrow3-x=2\)
\(\Rightarrow x=1\)
Vậy \(x=1\)
8)\(4.5^x-3=97\)
\(\Rightarrow4.5^x=100\)
\(\Rightarrow5^x=25\)
\(\Rightarrow5^x=5^2\)
\(\Rightarrow x=2\)
Vậy \(x=2\)
9)\(171-3.2^x=123\)
\(\Rightarrow3.2^x=48\)
\(\Rightarrow2^x=16\)
\(\Rightarrow2^x=2^4\)
\(\Rightarrow x=4\)
Vậy \(x=4\)
10)\(180-4.x^5=32\)
\(\Rightarrow4.x^5=148\)
\(\Rightarrow x^5=37\)//Đề có lỗi không ???
a , = 123+39-23 =(123-23) +39 =100+39 =139
b, = (64+36).32 = 100.32 =3200
c, =62.4 +5.2(5-1) =62.4 + 40 = 36.4+40 =144+40 +184
d, đề sao sao ấy nhể k rõ đề lm