(-3) (-5) (-6) (-10) -24^2
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ta có : (ghi lại đề)
=6+12+18+24+30/3+6+9+12+15
=2*(3/3+6/6+9/9+12/12+15/15)
=2*(1+1+1+1+1)
=2*5=10
chúc main học tốt nhé
25/7 - 2 + 3/2 = 43/14
4/5 x 10/3 : 8= 4/5 x 10/3 x 1/8 = 1/3
7/3 + 2/5 : 1/6 = 7/3+ 2/5 x 6 = 7/3 + 12/5 = 71/15
b)1/2*2/3*3/4*4/5*5/6*6/7*7/8*8/9*9/10
=1x2x3x4x5x6x7x8x9
2x3x4x5x6x7x8x9x10
= 1
10
A) \(\dfrac{5}{10}-\dfrac{2}{15}\)
\(=\dfrac{1}{2}-\dfrac{2}{15}\)
\(=\dfrac{15}{30}-\dfrac{4}{30}\)
\(=\dfrac{11}{30}\)
B)\(\dfrac{5}{20}-\dfrac{1}{6}\)
\(=\dfrac{1}{4}-\dfrac{1}{6}\)
\(=\dfrac{6}{24}-\dfrac{4}{24}\)
\(=\dfrac{2}{24}=\dfrac{1}{12}\)
C) \(\dfrac{6}{18}-\dfrac{6}{24}\)
\(=\dfrac{1}{3}-\dfrac{1}{4}\)
\(=\dfrac{4}{12}-\dfrac{3}{12}\)
\(=\dfrac{1}{12}\)
D) \(\dfrac{5}{9}-\dfrac{3}{12}\)
\(=\dfrac{5}{9}-\dfrac{1}{4}\)
\(=\dfrac{20}{36}-\dfrac{9}{36}\)
\(=\dfrac{11}{36}\).
a: =1/2-2/15
=15/30-4/30
=11/30
b: =1/4-1/6
=3/12-2/12
=1/12
c: =1/3-1/4
=1/12
d: =20/36-9/36
=11/36
e) 5(3-2x)+5(x-4)=6-4x
⇔15-10x+5x-20-6+4x=0
⇔-x-11=0
hay -x=11
⇔x=-11
Vậy: x=-11
g) 2(4x-8)-7(3+x)=|-4|(3-2)
⇔8x-16-21-7x=4
⇔x-37=4
hay x=41
Vậy: x=41
k) -7(5-x)-2(x-10)=15
⇔-35+7x-2x+20=15
⇔5x-15=15
hay 5x=30
⇔x=6
Vậy: x=6
m) -4(x+1)+(89x-3)=24
⇔-4x-4+89x-3=24
⇔85x-7=24
⇔85x=31
hay \(x=\frac{31}{85}\)(ktm x∈Z)
Vậy: x∈∅
q) 10(x-7)-8(x+5)=6*(-5)+24
⇔10x-70-8x-40=-6
⇔2x-110=-6
⇔2x=104
hay x=52
Vậy: x=52
\(\frac{1}{9\cdot10}+\frac{2}{10\cdot12}+\frac{3}{12\cdot15}+\frac{4}{15\cdot19}+\frac{5}{19\cdot24}+\frac{6}{24\cdot30}
\)
\(=\frac{1}{9}-\frac{1}{10}+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{15}+\frac{1}{15}-\frac{1}{19}+\frac{1}{19}-\frac{1}{24}+\frac{1}{24}-\frac{1}{30}\)
\(=\frac{1}{9}-\frac{1}{30}\)
\(=\frac{10}{90}-\frac{3}{90}\)
\(=\frac{7}{90}\)
a) n(n+2)
b) (3n-2)3n
c) ( 1) 1 n n 2
d) 1+n2 e) n(n+5)
f) (3n-2)(3n+1)
g) n ( n 3) 2 n n
h) ( 1)( 2) 2
i) n ( n 1)( n 2)