10+9-8+7-6+5-4+3-2+1-0

= 10 +[(9 - 8) + (7 - 6) + (5 - 4) + (3 - 2) + (1 - 0)]

= 10 + [1 + 1 + 1 + 1 + 1]

= 10 + 1 x 5

= 10 + 5

= 15

15

Số số hạng của dãy số là:

10-0+1=11(số)

Tổng của dãy số là: \(\left(10+0\right)\times\frac{11}{2}=10\times\frac{11}{2}=5\times11=55\)

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1+2+3+4+5+6+7+8+9+10+11=66

1+2+3+4+5+6+7+8+9+10+11=66

[(1+9)+(2+8)+(3+7)+(4+6)+5]x2

=(10+10+10+10+5)x2

=45x2

=90

50x2+2x10

=2x(50+10)

=2x60

=120

\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

Tui không biết nha giúp tui làm

550 bạn nhé

1+2+3+4=5+6+7+8+9+10

=(1+9)+(2+8)+(3+7)+(4+6)+(5+10)

= 10+10+10+10+10+15

= 55

1+2+3+4+5+6+7+8+9+10=55

\(a,2\times3=6\)

\(6\times2=12\)

\(10\times2=20\)

\(1\times2=2\)

\(b,5\times7=35\)

\(9\times5=45\)

\(5\times8=40\)

\(1\times5=5\)

5+6+7+8+9

=35

5+6+7+8+9+10

=45

0 nha :3

1 + 1 - 2 + 14 - 4 + 20 - 15 + 10 - 5 + 100 - 60 x 2

= (1 + 1 - 2) + (14 - 4) + (20 - 10) + (15 - 5) + 100 - 120

= (2 - 2) + 10 + 10 + 10 + 100 - 120

= 130 - 120

= 10

a. tổng số viên bi là ;

5+8+2+10 = 25

vậy tổng có 25 viên bi

b . lphần trăm lấy được viên bi vàng là 2/25

.

20

2/25 nha :>