bien doi ve trai ta duoc

(a+b)(a^2-ab+b^2)(a-b)(a^2+ab+b^2)=a^3+b^3+a^3-b^3=2a^3=VP(dpcm)

còn thíu 1 vs 90 nha

11*89=979

15*11=165

8x9:2

=72:2

=36

\(\frac{15}{4}+\frac{15}{28}+\frac{15}{70}+...+\frac{15}{x.\left(x+3\right)}=\frac{99}{20}\)

=> \(5.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{x.\left(x+3\right)}\right)=\frac{99}{20}\)

=> \(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{x}-\frac{1}{x+3}=\frac{99}{20}:5\)

=> \(1-\frac{1}{x+3}=\frac{99}{20}.\frac{1}{5}=\frac{99}{100}\)

=> \(\frac{1}{x+3}=1-\frac{99}{100}\)

=> \(\frac{1}{x+3}=\frac{1}{100}\)

=> x + 3 = 100

=> x = 100 - 3

=> x = 97

Tổng bằng:

4+5=9

Đáp số:9

\(-\frac{9}{25}.\frac{53}{3}-\left(\frac{-3}{5}\right)^2.\frac{22}{3}\)

\(=-\frac{159}{25}-\frac{9}{25}.\frac{22}{3}\)

\(=\frac{-159}{25}-\frac{66}{25}\)

\(=-9\)

Tổng bằng:

5+15=20

Đáp số: 20

ĐÁP SỐ : 5/9

Tổng bằng:

6+6+5+3+0=20

Đáp số:20