chịu

ok

2x10=20

3x10=30

chúc bạn học giỏi nhé

(0,3-3/20)x1 và 1/2

=3/10-

2x10=20 Vì 2x10=>2+2+2+2+2+2+2+2+2+2=20

3x10=30 Vì 3x10=>3+3+3+3+3+3+3+3+3+3=30

 chúc em đạt học sinh giỏi nhé

a) $5^6:5^5+{\left(\genfrac{}{}{0ex}{}{4}{9}\right)}^0=5^{6-5}+1=5+1=6$

b) ${\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{21}:{\left(1-\genfrac{}{}{0ex}{}{40}{49}\right)}^3$

$={\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{21}:{\left(\genfrac{}{}{0ex}{}{9}{49}\right)}^3$

$={\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{21}:{\left[{\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^2\right]}^3$

$={\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{21}:{\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^6$

$={\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{21-6}={\left(\genfrac{}{}{0ex}{}{3}{7}\right)}^{15}$

c) ${\left(\genfrac{}{}{0ex}{}{2}{3}\right)}^3-{\left(\genfrac{}{}{0ex}{}{-52}{3}\right)}^0+\genfrac{}{}{0ex}{}{4}{9}$

$=\genfrac{}{}{0ex}{}{8}{27}-1+\genfrac{}{}{0ex}{}{4}{9}$

$=\genfrac{}{}{0ex}{}{8-27+12}{27}=-\genfrac{}{}{0ex}{}{7}{27}$
 

B)(-3/4+5/13):2/7-(9/4-8/13):2/7

=(-19/52-85/52):2/7

=-2:2/7

=-7

A) -15,5 x 20,8 +2,5 x 9,2 -15,5 x 9,2 + 3,5 x 20,8

=-15,5 x 20,8 + 2,5 x 9,2 + -15,5 x 9,2 +3,5 x 20,8

=[20,8x(-15,5+3,5)]+[9,2x(2,5+-15,5)]

=[20,8x(-12)]+[9,2x(-13)]

=-249,6+-119,6

=-369,2

3

A=1x2x3x4+2x3x4x5+3x4x5x6+...+97x98x99x100

5xA=1x2x3x4+2x3x4x5x(6-1)+3x4x5x6x(7-2)+...+97x98x99x100x(101-96)

5xA=1x2x3x4x5+2x3x4x5x6-1x2x3x4x5+3x4x5x6x7-2x3x4x5x6+...+97x98x99x100x101-96x97x98x99x100

5xA=97x98x99x100x101

A=97x98x99x101x20=1901009880