tìm số dư
a) a=1+2+22+23+24+25+...+22017 : 7
b) b=7+72+73+74+75+76+...+72017 :399
Giải thích
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Sửa đề: \(\dfrac{74-x}{26}+\dfrac{75-x}{25}+\dfrac{76-x}{24}+\dfrac{77-x}{23}+\dfrac{78-x}{22}=-5\)Ta có: \(\dfrac{74-x}{26}+\dfrac{75-x}{25}+\dfrac{76-x}{24}+\dfrac{77-x}{23}+\dfrac{78-x}{22}=-5\)
\(\Leftrightarrow\dfrac{74-x}{26}+1+\dfrac{75-x}{25}+1+\dfrac{76-x}{24}+1+\dfrac{77-x}{23}+1+\dfrac{78-x}{22}+1=0\)
\(\Leftrightarrow\dfrac{100-x}{26}+\dfrac{100-x}{25}+\dfrac{100-x}{24}+\dfrac{100-x}{23}+\dfrac{100-x}{22}=0\)
\(\Leftrightarrow\left(100-x\right)\left(\dfrac{1}{26}+\dfrac{1}{25}+\dfrac{1}{24}+\dfrac{1}{23}+\dfrac{1}{22}\right)=0\)
mà \(\dfrac{1}{26}+\dfrac{1}{25}+\dfrac{1}{24}+\dfrac{1}{23}+\dfrac{1}{22}>0\)
nên 100-x=0
hay x=100
Vậy: S={100}
Ta có : \(\dfrac{74-x}{26}+\dfrac{75-x}{25}+\dfrac{76-x}{24}+\dfrac{77-x}{23}+\dfrac{78-x}{22}=-5\)
\(\Leftrightarrow\dfrac{74-x}{26}+\dfrac{75-x}{25}+\dfrac{76-x}{24}+\dfrac{77-x}{23}+\dfrac{78-x}{22}+5=0\)
\(\Leftrightarrow\dfrac{74-x}{26}+1+\dfrac{75-x}{25}+1+\dfrac{76-x}{24}+1+\dfrac{77-x}{23}+1+\dfrac{78-x}{22}+1=0\)
\(\Leftrightarrow\dfrac{100-x}{26}+\dfrac{100-x}{25}+\dfrac{100-x}{24}+\dfrac{100-x}{23}+\dfrac{100-x}{22}=0\)
\(\Leftrightarrow\left(100-x\right)\left(\dfrac{1}{26}+\dfrac{1}{25}+\dfrac{1}{24}+\dfrac{1}{23}+\dfrac{1}{22}\right)=0\)
Thấy : \(\dfrac{1}{26}+\dfrac{1}{25}+\dfrac{1}{24}+\dfrac{1}{23}+\dfrac{1}{22}\ne0\)
\(\Rightarrow100-x=0\)
\(\Leftrightarrow x=100\)
Vậy ...
Bài 1:
a. $=(-25)(-4)(-35)=100(-35)=-3500$
b. $=16-10=6$
c. $=180-(-16)-(-36)=180+16+36=232$
d. $=250-200:[1(-3)^2+(-8)]$
$=250-200:(9-8)=250-200=50$
2.
$60+2(12-x)=-48$
$2(12-x)=60-(-48)=60+48=108$
$12-x=108:2=54$
$x=12-54=-42$
Bài 1:
a. $=(-25)(-4)(-35)=100(-35)=-3500$
b. $=16-10=6$
c. $180-(-16)-(-36)=180+16+36=196+36=232$
d. $=250-200:[2000.(-3).2-6]$
$=250-200:[2000.(-6)+(-6)]$
$=250-200:[(-6)(2000+1)]=250-200[(-6).2001]$
$=250+200.6.2001=250+2401200=2401450$
Bài 2:
$60+2(12-x)=-48$
$2(12-x)=-48-60=-108$
$12-x=-108:2=-54$
$x=12-(-54)=66$
Bài 1:
\(a,A=\left(2+2^2\right)+\left(2^3+2^4\right)+...+\left(2^{2009}+2^{2010}\right)\\ A=\left(1+2\right)\left(2+2^3+...+2^{2009}\right)=3\left(2+...+2^{2009}\right)⋮3\\ A=\left(2+2^2+2^3\right)+...+\left(2^{2008}+2^{2009}+2^{2010}\right)\\ A=\left(1+2+2^2\right)\left(2+...+2^{2008}\right)=7\left(2+...+2^{2008}\right)⋮7\)
\(b,\left(\text{sửa lại đề}\right)B=\left(3+3^2\right)+\left(3^3+3^4\right)+...+\left(3^{2009}+3^{2010}\right)\\ B=\left(1+3\right)\left(3+3^3+...+3^{2009}\right)=4\left(3+3^3+...+3^{2009}\right)⋮4\\ B=\left(3+3^2+3^3\right)+...+\left(3^{2008}+3^{2009}+3^{2010}\right)\\ B=\left(1+3+3^2\right)\left(3+...+3^{2008}\right)=13\left(3+...+3^{2008}\right)⋮13\)
Bài 2:
\(a,\Rightarrow2A=2+2^2+...+2^{2012}\\ \Rightarrow2A-A=2+2^2+...+2^{2012}-1-2-2^2-...-2^{2011}\\ \Rightarrow A=2^{2012}-1>2^{2011}-1=B\\ b,A=\left(2020-1\right)\left(2020+1\right)=2020^2-2020+2020-1=2020^2-1< B\)
\(\frac{74-x}{26}+\frac{75-x}{25}+\frac{76-x}{24}+\frac{77-x}{23}+\frac{78-x}{22}=-5\)
\(\frac{74-x}{26}+1+\frac{75-x}{25}+1+\frac{76-x}{24}+1+\frac{77-x}{23}+1+\frac{78-x}{22}=-5+5\)
\(\frac{74-x}{26}+\frac{26}{26}+\frac{75-x}{25}+\frac{25}{25}+\frac{76-x}{24}+\frac{24}{24}+\frac{77-x}{23}+\frac{23}{23}+\frac{78-x}{22}+\frac{22}{22}=0\)
\(\frac{100-x}{26}+\frac{100-x}{25}+\frac{100-x}{24}+\frac{100-x}{23}+\frac{100-x}{22}=0\)
\(\left(100-x\right)\left(\frac{1}{26}+\frac{1}{25}+\frac{1}{24}+\frac{1}{23}+\frac{1}{22}\right)=0\)
=>100-x=0 ( \(\left(\frac{1}{26}+\frac{1}{25}+\frac{1}{24}+\frac{1}{23}+\frac{1}{22}\right)\ne0\))
x=100
hahaha
71 + 72 + 73 + 74 + 75 + 76 + 77 + 78 + 79
= ( 71 + 79 ) + ( 72 + 78 ) + ( 73 + 77 ) + ( 74 + 76 ) + 75
= 150 + 150 + 150 + 150 + 75
= 150 x 4 + 75
= 600 + 75
= 675
Tìm x :
X x 7 + X x 2 = 108
X x ( 7 + 2 ) = 108
X x 9 = 108
X = 108 : 9
X = 12
\(71+72+73+74+75+76+77+78+79\)
\(=\left(71+79\right)+\left(72+78\right)+\left(73+77\right)+\left(74+76\right)+75\)
\(=150+150+150+150+75\)
\(=600+75\)
\(=675\)
\(X\)x\(7+X\)x\(2=108\)
\(X\)x\(\left(7+2\right)=108\)
\(X\)x\(9=108\)
\(X=108:9\)
\(X=12\)
Vậy \(X=12\)
72, Let’s go to the cinema tonight.
Shall ………………… we go to the cinema tonight?………………
73, What is your weight?
How ……heavy are you?……………………………………………………
74, What a lovely cat!
How………………………… lovely the cat is!……………………………………
75, 1, Nam will be eighteen next month.
It will be ……………… Nam's eighteenth birthday next month.…………………………………………
76, When is your birthday?
What is ………………… your date of birth?………………………………………
77, Where were you born?
What is …………………… your birthplace?……………………………………
78, Hoang will be eighteen next month.
It will be ………………… Hoang's eighteenth birthday next month.………………………………………
79, It takes me two hours to get to Hanoi by motorbike.
I spend …………………… two hours getting to Hanoi by motorbike.……………………………………
80, My house is smaller than his one.
His house ……… is bigger than my house.………………………………………………
81, She is able to speak English to her teacher.
She can ……………… speak English to her teacher.…………………………………………
82, The black car is cheaper than the red one
The red car ………………… is more expensive than the black one…………………………………………………
72, Let’s go to the cinema tonight.
Shall we go to the cinema tonight?………………………………… 73, What is your weight? How heavy are you………………………………………………………… 74, What a lovely cat! How lovely the cat is……………………………………………………………… 75, 1, Nam will be eighteen next month. It will be Nam's eighteenth birthday next month………………………………………………………… 76, When is your birthday? What is your birthday'day?………………………………………………………… 77, Where were you born? What is your hometown………………………………………………………… 78, Hoang will be eighteen next month. It will be Hoang's eighteenth birthday next month………………………………………………………… 79, It takes me two hours to get to Hanoi by motorbike. I spend 2 hours getting to HN by bike………………………………………………………… 80, My house is smaller than his one. His house is bigger than my……………………………………………………… 81, She is able to speak English to her teacher. She can speak English to her teacher………………………………………………………… 82, The black car is cheaper than the red one The red car is more expensive than the black one……………………………………………………………………