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\(A=\left(3,1-2,5\right)-\left(-2,5+3,1\right)\)
\(A=3,1-2,5+2,5-3,1\)
\(A=\left(3,1-3,1\right)-\left(2,5-2,5\right)\)
\(A=0-0\)
\(A=0\)
\(B=\left(5,3-2,8\right)-\left(4+5,3\right)\)
\(B=5,3-2,8-4-5,3\)
\(B=\left(5,3-5,3\right)-\left(2,8+4\right)\\ B=0-6,8\\ B=-6,8\)
1a, (-3,8) + [ (-5,7)+3,8]
= (-3,8+3,8) -5,7
= -5,7
b, 31,4 +[6,4 +(-18)]
= 31,4 - 11,6
= 19,8
c,[(9,6 )+4,5 ] +[9,6 +(-1,5)]
= 9,6 +9,6 +(4,5-1,5)
= 19,2 +3
=22,2
d, [ (-4,9) + (-7,8)] +[1,9+2,8]
= (-4,9 +1,9)+ (-7,8+2,8)
= -3 -5
=-8
e, (3,1-2,5)-(-2,5+3,1)
= (3,1-3,1)+(2,5-2,5)
=0
f, (5,3 -2,8 )- (4+5,3)
= (5,3-5,3) -2,8-4
= -6,8
g, -(251,3 +281 )+ 3,251 -(1-281)
= -251,3-281+3,251 -1+281
= (-281+281) -251,3 +3,251 -1
= -249,049
h,-(3/54+3/4)-(-3/4 +2/5)
= -3/54-3/4 +3/4 +2/5
=(-3/4+3/4) -3/54 +2/5
=123/270
chúc bạn học tốt
a) \(\left|2,5-x\right|-1,3=0\)
th1: \(2,5-x\ge0\Leftrightarrow x\le2,5\)
\(\Rightarrow\left|2,5-x\right|-1,3=0\Leftrightarrow2,5-x-1,3=0\Leftrightarrow x=1,2\left(tmđk\right)\)
th2: \(2,5-x< 0\Leftrightarrow x>2,5\)
\(\Rightarrow\left|2,5-x\right|-1,3=0\Leftrightarrow x-2,5-1,3=0\Leftrightarrow x=3,8\left(tmđk\right)\)
vậy \(x=1,2;x=3,8\)
b) \(1,6.\left|x-0,2\right|=0\Leftrightarrow\left|x-0,2\right|=0\Leftrightarrow x-0,2=0\Leftrightarrow x=0,2\) vậy \(x=0,2\)
c) \(\left|\dfrac{1}{3}-x\right|-\left|\dfrac{-3}{7}\right|=0\)
th1: \(\dfrac{1}{3}-x\ge0\Leftrightarrow x\le\dfrac{1}{3}\)
\(\Rightarrow\left|\dfrac{1}{3}-x\right|-\left|\dfrac{-3}{7}\right|=0\Leftrightarrow\dfrac{1}{3}-x-\dfrac{3}{7}=0\Leftrightarrow x=\dfrac{-2}{21}\left(tmđk\right)\)
th2: \(\dfrac{1}{3}-x< 0\Leftrightarrow x>\dfrac{1}{3}\)
\(\Rightarrow\left|\dfrac{1}{3}-x\right|-\left|\dfrac{-3}{7}\right|=0\Leftrightarrow x-\dfrac{1}{3}-\dfrac{3}{7}=0\Leftrightarrow x=\dfrac{16}{21}\left(tmđk\right)\)
vậy \(x=\dfrac{-2}{21};x=\dfrac{16}{21}\)
d) \(\left|x+\dfrac{4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\)
th1: \(x+\dfrac{4}{15}\ge0\Leftrightarrow x\ge\dfrac{-4}{15}\)
\(\Rightarrow\left|x+\dfrac{4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\Leftrightarrow x+\dfrac{4}{15}-3,75=-2,15\)
\(\Leftrightarrow x=\dfrac{4}{3}\left(tmđk\right)\)
th2: \(x+\dfrac{4}{15}< 0\Leftrightarrow x< \dfrac{-4}{15}\)
\(\Rightarrow\left|x+\dfrac{4}{15}\right|-\left|-3,75\right|=-\left|-2,15\right|\Leftrightarrow-x-\dfrac{4}{15}-3,75=-2,15\)
\(\Leftrightarrow x=\dfrac{-28}{15}\left(tmđk\right)\)
vậy \(x=\dfrac{4}{3};x=\dfrac{-28}{15}\)
e) ta có : \(\left|x-1,5\right|\ge0\forall x\) và \(\left|2,5-x\right|\ge0\forall x\)
\(\Rightarrow\left|x-1,5\right|+\left|2,5-x\right|=0\Leftrightarrow\left\{{}\begin{matrix}x-1,5=0\\2,5-x=0\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=1,5\\x=2,5\end{matrix}\right.\) 2 giá trị này khác nhau \(\Rightarrow\) phương trình vô nghiệm
A = \(\left(3,1-2,5\right)-\left(-2,5+3,1\right)\)
\(=3,1-2,5+2,5-3,1=6,2\)
B = \(\left(5,3-2,8\right)-\left(4+5,3\right)\)
\(=5,3-2,8-4-5,3=-6,8\)
C = \(-\left(251.3+281\right)+3.251-\left(1-281\right)\)
\(=-251.3-281+3.251-1+281=-1\)
D = \(-\left(\frac{3}{5}+\frac{3}{4}\right)-\left(-\frac{3}{4}+\frac{2}{5}\right)\)
\(=-\frac{3}{5}-\frac{3}{4}+\frac{3}{4}-\frac{2}{5}=-1\)
(Nhớ k cho mình với nhá!)
làm bài 3 BĐT
theo bảng xét dấu
còn bài 1,2 ở trên là 1.1 và 1.2 đều trg bài 1.2
bài 1.2 (tức bài 2 ở trên )làm a,b,c,d
\còn bài 2( tức bài 2 ở trên) làm hết
a) \(\left(\dfrac{1}{5}\right)^5.5^5=\left(\dfrac{1}{5}.5\right)^5=1^5=1\)
b) \(\left(0,125\right)^3.512=\left(0,512\right)^3.8^3=\left(0,512.8\right)^3=1^3=1\)
c) \(\left(0,25\right)^4.1024=\left[\left(0,25\right)^2\right]^2.32^2=\left(\dfrac{1}{6}\right)^2.32^2=\left(\dfrac{1}{6}.32\right)^2=2^2=4\)
d) \(\dfrac{120^3}{40^3}=\left(\dfrac{120}{40}\right)^3=3^3=64\)
e) \(\dfrac{390^4}{130^4}=\left(\dfrac{390}{130}\right)^4=3^4=81\)
g) \(\dfrac{3^2}{\left(0,375\right)^2}=\left(\dfrac{3}{0,375}\right)^3=8^3=512\)
a)\(3,8:\left(2x\right)=\dfrac{1}{4}:2\dfrac{2}{3}\)
\(2x=3,8:\dfrac{3}{32}\)
\(x=\dfrac{608}{15}:2\)
\(x=\dfrac{304}{15}\)
b)\(\left(0,25x\right):3=\dfrac{5}{6}:0,125\)
\(0,25x=\dfrac{20}{3}\times3\)
\(x=20:0,25\)
\(x=80\)
c) \(0,01:2,5=\left(0,75\times x\right):0,75\)
\(0,004=0,75\times x:0,75\)
\(0,004=x\times0,75:0,75\)
\(0,004=x\times1\)
\(0,004=x\)
\(\Rightarrow x=0,004\)
d)\(1\dfrac{1}{3}:0,8=\dfrac{2}{3}:\left(0,1x\right)\)
\(\dfrac{5}{3}=\dfrac{2}{3}:0,1\times x\)
\(\dfrac{5}{3}=\dfrac{20}{3}\times x\)
\(\Rightarrow x=\dfrac{20}{3}:\dfrac{5}{3}\)
\(x=4\)
a) \(x=20\dfrac{4}{15}.\)
b) \(x=80\)
c) \(x=0,004\)
d) \(x=4.\)
Tính nhanh:
a) (-6,37 × 0,4) × 2,5;
b) (-0,125) × (-5,3) × 8;
c) (-2,5) × (-4) × (-7,9);
d) (-0,375) × 413(−2)3413(−2)3
Hướng dẫn làm bài:
a) (- 6,37 × 0,4) × 2,5
= - 6,37× (0,4 × 2,5)
= - 6,37 × 1 = - 6,37
b) (-0,125) × (-5,3) × 8
= (-0,125 × 8) × (-5,3)
=(-1). (-5,3) = 5,3
c) (-2,5) × (-4) × (-7,9)
= [(-2,5) × (-4)] × (-7,9)
= 10 . (-7,9)
= -79
d) (−0,375).413.(−2)3
=[(−0,375).(−8)].133=[(−0,375).(−8)].133
=3.133=13