80^2-75^2+70^2-65^2+60^2-....+10^2-5^2
Những câu hỏi liên quan
Tính nhanh: 802-752+702-652+602-552+........+102-52
\(=\left(80-75\right)\left(80+75\right)+\left(70-65\right)\left(75+65\right)+...+\left(10-5\right)\left(10+5\right)\)
\(=5\cdot155+5\cdot135+..+5\cdot15\)
\(=5\cdot\left(155+135+...+15\right)\)
\(=5\cdot\left(155+15+135+35+115+55+95+75\right)\)
\(=5\cdot\left(170\cdot4\right)\)
\(=5\cdot680=3400\)
802 - 752 + 702 - 652 + 602 - 552 + ... + 102 - 52
= ( 802 - 752 ) + ( 702 - 652 ) + ( 602 - 552 ) + ... + ( 102 - 52 )
= ( 80 - 75 )( 80 + 75 ) + ( 70 - 65 )( 70 + 65 ) + ... + ( 10 - 5 )( 10 + 5 )
= 5.155 + 5.135 + ... + 5.15
= 5( 155 + 135 + ... + 15 )
= \(5\left\{\frac{\left(155+15\right)\left[\left(155-15\right):20+1\right]}{2}\right\}\)
= 5.680
= 3400
12{390:[500-(125+35.7)]}
70-[60-(12-8)2]
32.7-(110+24):52
2.Tìm x
80-(4.52-3.23)=210-(x-4)
(17.x-25):8+65=92
1) 168 - ( 18 - 2x ) x 12 = 120
2) [ 75 + ( 16 - x ) ] x 2 = 156
3) 124 - 24 x ( 3x - 16 ) = 76
4) [ ( 10 - x ) x 2 + 5 ] : 3 - 2 = 3
5) [ 80 + ( 62 - x ) ] : 17 - 7 = 1
6) 65 - ( 5x - 70 ) : 2 = 50
7) 504 : 9 136 - 2x ) + 4 = 32
8) ( 13x - 28 ) x 15 - 5 x 23 = 320
Mình cần gấp ạ !!!
A)1/10+4/20+9/30+25/50+36/60+49/70+64/80+81/90
B)2/3*5+2/5*7+2/7*9+...2/41*43
\(B=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{41.43}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{41}-\frac{1}{43}\)
\(=\frac{1}{3}-\frac{1}{43}\)
\(=\frac{40}{129}\)
p/s: chúc bạn học tốt
Đúng 0
Bình luận (0)
Tìm x:
a) 2^x+70=74
b)120-4x:2=80
c)(3x+5)^2=400
d)5(x+7)^3=135
e)600-{100-[60+(x^3+10)]}=518
g){[(16x-30).8]+80}:5=224
a. 2x + 70 = 74
<=> 2x = 4
<=> x = 2
b. 120 - \(\dfrac{4x}{2}\) = 80
<=> 120 - 2x = 80
<=> 120 - 80 = 2x
<=> 2x = 40
<=> x = 20
c. (3x + 5)2 = 400
<=> \(|3x+5|=\sqrt{400}\)
<=> \(|3x+5|=20\)
<=> \(\left[{}\begin{matrix}3x+5=20\\3x+5=-20\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\dfrac{-25}{3}\end{matrix}\right.\)
Đúng 0
Bình luận (0)
1+2+3+4+5+6+7+8+9=
2+2+2+2+2+2+2+2+2+2=
10+20+30+49+50+60+70+80+90=
Kb nhaaaaa hjjjjjj mk tk chooo
1+2+3+4+5+6+7+8+9= 45
2+2+2+2+2+2+2+2+2+2= 20
10+20+30+49+50+60+70+80+90= 459
Đúng 0
Bình luận (0)
1+2+3+4+5+6+7+8+9=45
2+2+2+2+2+2+2+2+2+2=20
10+20+30+40+50+60+70+80+90=450
Học tốt tích rồi mình kết bạn cho
Đúng 0
Bình luận (0)
1+2+3+4+5+6+7+8+9=45
2+2+2+2+2+2+2+2+2+2=20
10+20+30+49+50+60+70+80+90=450
Đúng 0
Bình luận (0)
Xem thêm câu trả lời
bài 2:Tính nhanh biểu thức:
70-65+60-55+50-45+....+20-15+10-5
Bài 2: = 7 tổng mỗi tổng = 5
Vậy . 5 x 7 = 35
Đúng 0
Bình luận (0)
70-65+60-55+50-45+...+20-15+10-5
=(70-65)+(60-55)+(50-45)+...+(20-15)+(10-5)
= 5 + 5 + 5 +...+ 5 + 5
= 5x7
= 35.
Đúng 0
Bình luận (0)
1+2+3+4+5+6+7+8+9+0+1-2-3-4-4-5-6-7-8-9-0+10+20+30+40+50+60+70+80+90=
(1+9)+(2+8)+(3+7)+(4+6)+(5+5)+(6+4)+(7+3)+(8+2)+(10+90)+(20+80)+(30+70)+(40+60)+(50+50)+(40+60)+(30+70)+(20+80) =10+10+10+10+10+10+10+10+100+100+100+100+100+100+100+100=(10x8)+(100x8) = 80 + 800 =880
Tick vs ah
Đúng 0
Bình luận (0)
1=10 2=20 3=3= 4=40 5=50 6=60 7=70 8=80 9=90 10=?
Xem thêm câu trả lời