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bài 1 tính giá trị biểu thức
( - 25 ) nhân ( -3 ) nhân x với x = 4
\(\left(-25\right).\left(-3\right).4\)
\(=\left(-25\right).4.\left(-3\right)\)
\(=-100.\left(-3\right)=300\)
( -1 ) nhân ( -4 ) nhân 5 nhân 8 nhân y với y =25
\(\left(-1\right).\left(-4\right).5.8.25\)
\(=4.5.8.25=4.25.5.8\)
\(=100.40=40000\)
( 2ab mũ 2 ) : c với a =4 ; b= -6 ; c =12
\(\left(2.4.\left(-6\right)\right)^2:12\)
\(=\left(-48\right)^2:12\)
\(=2304:12=192\)
[ ( -25 ) nhân ( - 27 ) nhân ( -x ) ] : y với x = 4 ; y = -9
\(\left[\left(-25\right).\left(-27\right).\left(-4\right)\right]:-9\)
\(=-2700:\left(-9\right)\)
\(=300\)
(a mũ 2 _ b mũ 2) : ( a + b ) nhân ( a _ b ) với a + 5 , b = -3
\(\left(5^2-\left(-3\right)^2\right):\left(5-3\right).\left(5+3\right)\)
\(=16:2.8\)
\(=8.8=64\)
\(5.\left(x+35\right)=515\)
\(x+35=515:5\)
\(x+35=103\)
\(x=103-35\)
\(\Rightarrow x=68\)
\(\left(x+40\right).15=75.12\)
\(\Rightarrow\left(x+40\right)=5.12\)[ rút gọn theo t/c đẳng thức ]
\(x+40=60\)
\(x=20\)
1) \(2^x-15=17\)
\(\Leftrightarrow2^x=32=2^5\)
\(\Rightarrow x=5\)
2) \(\left(7x-11\right)^3=25\cdot5^2+200\)
\(\Leftrightarrow\left(7x-11\right)^3=825\)
\(\Leftrightarrow7x-11=\sqrt[3]{825}\)
\(\Leftrightarrow7x=11+\sqrt[3]{825}\)
\(\Rightarrow x=\frac{11+\sqrt[3]{825}}{7}\)
3) \(\left(x+1\right)^{100}-3\left(x+1\right)^{99}=0\)
\(\Leftrightarrow\left(x+1\right)^{99}\left(x-2\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}\left(x+1\right)^{99}=0\\x-2=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=-1\\x=2\end{cases}}\)
4) \(4x+5\left(x+3\right)=105\)
\(\Leftrightarrow9x+15=105\)
\(\Leftrightarrow9x=90\)
\(\Rightarrow x=10\)
5) \(5\cdot\left(x-2\right)+10\left(x+3\right)=170\)
\(\Leftrightarrow5\left[x-2+2\left(x+3\right)\right]=170\)
\(\Leftrightarrow3x+4=34\)
\(\Leftrightarrow3x=30\)
\(\Rightarrow x=10\)
\(\frac{10}{3}.x+\frac{67}{4}=\frac{53}{4}\)
\(\frac{10}{3}.x=\frac{53}{4}-\frac{67}{4}\)
\(\frac{10}{3}.x=-\frac{7}{2}\)
\(x=-\frac{7}{2}:\frac{10}{3}\)
\(x=-\frac{21}{20}\)
\(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
Đặt \(A=\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...+\frac{20}{53.55}\)
\(A=\frac{10.2}{11.13}-\frac{10.2}{13.15}-\frac{10.2}{15.17}-...-\frac{10.2}{53.55}\)
\(A=10\left(\frac{2}{11.13}-\frac{2}{13.15}-\frac{2}{15.17}-...-\frac{2}{53.55}\right)\)
\(A=10\left(\frac{1}{11}-\frac{1}{55}\right)\)
\(A=10.\frac{4}{55}\)
\(A=\frac{40}{55}\)\(A=10.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\)
câu 1 bỏ dấu ngoặc rồi tính
( 36 + 79 ) + ( 145 _ 79 _ 36 )
\(=36+79+145-79-36\)
\(=\left(36-36\right)+\left(79-79\right)+145\)\
\(=0+0+145=145\)
10 _ [ 12 _ ( -9 _ 1 ) ]
\(=10-12-10\)
\(=10-10-12\)
\(=0-12=-12\)
( 38 _ 29 + 43) _ ( 43 + 38 )
\(=38-29+43-43-38\)
\(=\left(38-38\right)+\left(43-43\right)-29\)
\(=0+0-29=-29\)
271 _ [ ( -43 ) + 271 _ ( -17 ) ]
\(=271+43-271-17\)
\(=\left(271-271\right)+\left(43-17\right)\)
\(=0+26=26\)
- 144 _ [ 29 _ ( + 144 ) _ ( + 144 )]
\(=-144-19+144+144\)
\(=\left(-144+144+144\right)-19\)
\(=144-19=125\)
đợi mk lm tiếp câu 2 nha .
bài 2 tính tổng các số nguyên
- 18 < hoặc bằng x < hoặc bằng 17
\(\Rightarrow x\in\left\{-18;-17;-16;....;17\right\}\)
tổng \(x=-18+\left(-17\right)+\left(-16\right)+...+17=-18\)
- 27 < hoặc bằng x < hoặc bằng 27
\(\Rightarrow x\in\left\{-27;-26;-25;..;27\right\}\)
Tổng \(x=-27+\left(-26\right)+\left(-25\right)+...+27=0\)
6 2/7 + 7 3/5 + 8 6/9 + 9 1/4 + 2/5 + 5/7 + 1/3 x 3/4 + 1967
= 44/7 + 38/5 + 78/9 + 37/4 + 2/5 + 5/7 + 1/3 + 1967
= ( 44/7 + 5/7 ) + ( 38/5 + 2/5 ) + ( 26/3 + 1/3 ) + ( 37/4 + 3/4 ) +1967
= 7 + 8 + 9 + 10 + 1967
= 15 + 9 + 10 + 1967
= 24 + 10 + 1967
= 34 + 1967
= 2001
\(\text{- ( 2789 _ 435 ) + ( 1789 _ 1435 )}\)
\(=-2789+435+1789-1435\)
\(=\left(-2789+1789\right)+\left(435-1435\right)\)
\(=-1000+-1000\)
\(=-2000\)
\(=-\left(-2010\right)+36.41-36.\left(-59\right)\)
\(=2010+36.\left(41+59\right)\)
\(=2010+36.100\)
\(=2010+3600\)
\(=5610\)
\(-75.\left(18-65\right)-65.\left(75-18\right)\)
\(=-75.18+75.65-65.75+65.18\)
\(=18.\left(-75+65\right)+75.\left(65-65\right)\)
\(=18.\left(-10\right)+75.0\)
\(=-180\)
\(-15:x=3\)
\(x=-15:3\)
\(x=-5\)
\(-3x+8=7\)
\(-3x=-1\)
\(x=\frac{1}{3}\)
\(\left(x-6\right).\left(7-x\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x-6=0\\7-x=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=6\\x=7\end{cases}}}\)
\(\Rightarrow x\in\left\{6;7\right\}\)
\(2.\left(x-3\right)-3.\left(x-5\right)=4.\left(3-x\right)-18\)
\(2x-6-3x+15=12-4x-18\)
\(2x-3x+4x=12-18-15+6\)
\(3x=-15\)
\(\Rightarrow x=-5\)
\(-a.\left(c-d\right)-d.\left(a+c\right)=-c.\left(a+d\right)\)
\(-a.c+a.d-d.a+-d.c=-c.\left(a+d\right)\)
\(-c.\left(a+d\right)+a.\left(d-d\right)=-c.\left(a+d\right)\)
\(-c.\left(a+d\right)+a.0=-c.\left(a+d\right)\)
\(\Rightarrow-c.\left(a+d\right)=-c.\left(a+d\right)\)
(3a+2).(2a–1)+(3–a).(6a+2)–17.(a–1)
=6a²−3a+4a−2+18a+6−6a²−2a−17a+17
=(6a²−6a²)+(−3a+4a+18a−2a−17a)+(17−2+6)
=0+0+21
=21
học tốt
1.53x201=10653
2.
a)4 xX-15x4=6x15+X
<=>4x-60=90+x
<=>4x-x=60+90
<=>3x=150
<=>x=50
b(102+28-2x):20-5=1
<=>(130-2x):20=6
<=>130-2x=120
<=>2x=10
<=>x=5
c)1999x-x=1999+1997+1999
<=>1998x=5995
<=>\(x\approx3\)
d)105-5x=150:15
<=>105-5x=10
<=>5x=95
<=>x=19
e)(x+1)+(x+2)+(x+3)+...+(x+6)=78
<=>6x+21=78
<=>6x=57
<=>x=9,5
1) 53x201=53x200+53=10600+53=10653
2a)
4x-15x4=6x15+x
4x-60=90+x
4x-x=90+60
3x=150
x=50
b) x=5
c) x=3
d)x=19
e) x=9,5