5,6x2 +2,8x8 +11,2x2 - 48,5

=5,6*2+9,6*2+11,2*2-24,25*2

=2*(5,6+9,6+11,2-24,25)

=2*2,15

=4,3

5,6x2 +2,8x8 +11,2x2 - 48,5
=5,6*2+9,6*2+11,2*2-24,25*2
=2*(5,6+9,6+11,2-24,25)
=2*2,15
=4,3
 

à ha !! cái này là tự hỏi tự trả lời gọi tắt là bị tự kỉ đó em (^_^)

=2,8X2X2+2,8X8+2,8X4X2-48,5                                                                                                                       =2,8X4+2,8X8+2,8X8-48,5                                                                                                                              =2,8X(4+8+8)-48,5                                                                                                                                         =2,8X20-48,5                                                                                                                                                 =56-48,5                                                                                                                                                       =7,5.            

5,6x2+2,8x8+11,2x2-48,5

=5,6x2+2,8x2x4+5,6x2x2-48,5

=5,6x2+5,6x4+5,6xx4-48,5

=5,6x(2+4+4)-48,5

=5,6x10-48,5

=56-48,5

=7,5

5,6 × 2 + 2,8 × 8 + 11,2 × 2 - 46

= 5,6 × 2 + 2,8 × 2 × 4 + 5,6 × 2 × 2 - 46

= 5,6 × 2 + 5,6 × 4 + 5,6 × 4 - 46

= 5,6 × (2 + 4 + 4) - 46

= 5,6 × 10 - 46

= 56 - 46

= 10

5,6 × 2 + 2,8 × 8 + 11,2 × 2 - 46

= 5,6 × 2 + 2,8 × 2 × 4 + 5,6 × 2 × 2 - 46

= 5,6 × 2 + 5,6 × 4 + 5,6 × 4 - 46

= 5,6 × (2 + 4 + 4) - 46

= 5,6 × 10 - 46

= 56 - 46

= 10

5,6x2+2,8x8+11,2x2-48,5

=5,6x2+2,8x2x4+5,6x2x2-48,5

=5,6x2+5,6x4+5,6x4-48,5

=5,6x(2+4+4)-48,5

=5,6x10-48,5

=56-48,5

=7,5

=2,8x2x2+2,8x8+2,8x4x2-48,5

=2,8x4+2,8x8+2,8x8-48,5

=2,8x(4+8+8)-48,5

=2,8x20-48,5

=56-48,5

=7,5

tích cho mình nha

\(d,\dfrac{5}{7}+\dfrac{9}{23}+-\dfrac{12}{7}+\dfrac{14}{23}\)

\(=\left(\dfrac{5}{7}+\dfrac{-12}{7}\right)+\left(\dfrac{9}{23}+\dfrac{14}{23}\right)\)

\(=-\dfrac{7}{7}+\dfrac{23}{23}\)

\(=\left(-1\right)+1=0\)

\(e,\dfrac{3}{17}+-\dfrac{5}{13}+-\dfrac{18}{35}+\dfrac{14}{17}+\dfrac{17}{-35}+-\dfrac{8}{13}\)

\(=\left(\dfrac{3}{17}+\dfrac{14}{17}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)+\left(\dfrac{-18}{35}+\dfrac{-17}{35}\right)\)

\(=\dfrac{17}{17}+\dfrac{-13}{13}+-\dfrac{35}{35}\)

\(=1+\left(-1\right)+\left(-1\right)=0+\left(-1\right)=-1\)

\(f,\dfrac{-3}{8}. \dfrac{1}{6}+\dfrac{3}{-8}.\dfrac{5}{6}+\dfrac{-10}{16}\)

\(=\dfrac{-3}{8}.\dfrac{1}{6}+\dfrac{-3}{8}.\dfrac{5}{6}+\dfrac{-10}{16}\)

\(=\dfrac{-3}{8}.\left(\dfrac{1}{6}+\dfrac{5}{6}\right)+-\dfrac{10}{16}\)

=\(\dfrac{-3}{8}.1+\dfrac{-10}{16}\)

\(=\dfrac{-3}{8}+\dfrac{-10}{16}\)

\(=\dfrac{-6}{16}+\dfrac{-10}{16}=\dfrac{-16}{16}=-1\)

\(g,\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{11}{-4}=\dfrac{-4}{11}.\dfrac{5}{15}.\dfrac{-11}{4}\)

\(=\left(\dfrac{-4}{11}.\dfrac{-11}{4}\right).\dfrac{5}{15}\)

\(=1.\dfrac{5}{15}=1.\dfrac{1}{3}=\dfrac{1}{3}\)

\(h,\dfrac{7}{36}-\dfrac{8}{-9}+\dfrac{-2}{3}=\dfrac{7}{36}-\dfrac{-8}{9}+\dfrac{-2}{3}\)

\(=\dfrac{7}{36}-\dfrac{-32}{36}+\dfrac{-24}{36}=\dfrac{7-\left(-32\right)+\left(-24\right)}{36}\)

\(=\dfrac{15}{56}=\dfrac{5}{12}\)

Tick mình nha ^^

d.\(\dfrac{5}{7}\)+\(\dfrac{9}{23}\)+\(\dfrac{12}{7}\)+\(\dfrac{14}{23}\)=(\(\dfrac{5}{7}\)+\(\dfrac{12}{7}\))+(\(\dfrac{9}{23}\)+\(\dfrac{14}{23}\))

                            =\(\dfrac{17}{7}\)+ 1 = \(\dfrac{24}{7}\)

e.\(\dfrac{3}{17}\)+\(\dfrac{-5}{13}\)+\(\dfrac{-18}{35}\)+\(\dfrac{14}{17}\)+\(\dfrac{17}{-35}\)+\(\dfrac{-8}{13}\)

=(\(\dfrac{3}{17}\)+\(\dfrac{14}{17}\))+(\(\dfrac{-5}{13}\)+\(\dfrac{-8}{13}\))+(\(\dfrac{-18}{35}\)+\(\dfrac{17}{-35}\))

= 1+ (-1) + (-1) = -1

f. \(\dfrac{-3}{8}\).\(\dfrac{1}{6}\)+\(\dfrac{3}{-8}\).\(\dfrac{5}{6}\)+\(\dfrac{-10}{16}\)=\(\dfrac{-3}{8}\)(\(\dfrac{1}{6}\)+\(\dfrac{5}{6}\)) + \(\dfrac{-5}{8}\)

                                   =\(\dfrac{-3}{8}\)+\(\dfrac{-5}{8}\)= -1

g. \(\dfrac{-4}{11}\).\(\dfrac{5}{15}\).\(\dfrac{11}{-4}\)=\(\dfrac{5}{15}\)

h.\(\dfrac{7}{36}\)-\(\dfrac{8}{-9}\)+\(\dfrac{-2}{3}\)= \(\dfrac{7}{36}\)-\(\dfrac{-32}{36}\)+\(\dfrac{-24}{36}\)

                       =\(\dfrac{-49}{36}\)

Dêện tích khu đất là 0,05 x 100 : 0,4 = 12,5 (ha)