a) \(...\Rightarrow\left[\left(x-2\right):2+1\right]\left(x+2\right):2=60\)

\(\Rightarrow\left[\dfrac{x-2}{2}+1\right]\left(x+2\right)=120\)

\(\Rightarrow\dfrac{x}{2}\left(x+2\right)=120\)

\(\Rightarrow x\left(x+2\right)=240\)

\(\Rightarrow x\in\varnothing\left(x\inℕ\right)\)

2+4+6+...+ x=60
(2+ X)x  x/2 =120
(2+X)x X = 120 x 2
2x X+X x X= 120
Vì x là số chẵn nên ta thử như sau
X=10   suy ra X x X+2 x X =100 +20=120  (đúng)
X=8      suy ra X x X+2 x X=64+16=80  (loại)
Suy ra X=10

(nếu X càng nhỏ hơn 8 thì đáp số không thể bằng 120)

a) \(\text{13 x 58 x 4 + 32 x 26 x 2 + 52 x 10 }\)

\(\text{=(13 x 4 ) x 58 + 32 x 13 x 2 x 2 + 13 x 4 x 10}\)

\(\text{= ( 13 x 4 ) x 58 + 32 x ( 13 x 2 x 2 ) + ( 13 x 4 ) x 10 }\)

\(\text{= 52 x 58 + 32 x 52 + 52 x 10}\)

\(\text{=52 x ( 58 + 32 + 10 )}\)

\(\text{=52 x 100 = 5200}\)

b) \(\text{14 x 35 x 5 + 10 x 25 x 7 + 20 x 70 x 2}\)

\(\text{= ( 14 x 5 ) x 35 + (10 x 7 ) x 25 + 20 x 70 x 2 }\)

\(\text{= 70 x 35 + 70 x 25 + 20 x 2 x 70 }\)

\(\text{= 70 x ( 35 + 25 + 40 )}\)

\(\text{= 70 x 100 = 7000 }\)

e) \(\text{5.3.37.4+5.24.21+21.5.12}\)

\(\text{= 5.(3.37.4+24.21+21.12)}\)

\(\text{= 5.1200}\)

\(=6000\)

\(=\dfrac{637.\left(526+1\right)-189}{526.637+448}=\dfrac{637.526+637-189}{526.637+446}=\dfrac{637.526+448}{526.637+448}=1\)

\(\left(637.527-189\right):\left(526.637+448\right)\)

\(=\left(335699-189\right):\left(335062+448\right)\)

\(=335510:335510\)

\(=1\)

Tổng các số ở nhóm chứa số 199 là :

\(\left[\left(199-1\right):2+1\right]\left(1+199\right):2=100.200:2=10000\)

Đáp số...

Bạn nên viết đề bằng công thức toán (biểu tượng $\sum$ góc trái khung soạn thảo) để mn hiểu đề của bạn hơn.

Độ dài cạnh BC là: 

  41 - ( 15 + 17) = 9 (cm)

Kết luận:..

Vì 2 góc \(\widehat{AOB}\) và \(\widehat{BOC}\) kề bù nên:

\(\widehat{AOB}+\widehat{BOC}=180^o\)

\(\Rightarrow25^o+\widehat{BOC}=180^o\)

\(\Rightarrow\widehat{BOC}=180^o-25^o=155^o\)

Vậy \(\widehat{BOC}=155^o\)

gải hộ với

\(12^7:6^7=\left(12:6\right)^7=2^7\)

đây nha

12⁷:6⁷

=(12:6)⁷

=2⁷

giúp mình với !!!!!!!!!!!!!!!!!!!!!!!!

Câu b, bài b1 chứng minh \(a=2^{2006}-1?\)

\(A=\dfrac{7}{1.9}+\dfrac{7}{9.17}+\dfrac{7}{17.25}+...+\dfrac{7}{81.89}\)

\(\dfrac{8}{7}A=\dfrac{8}{1.9}+\dfrac{8}{9.17}+\dfrac{8}{17.25}+...+\dfrac{8}{81.89}\)

\(\dfrac{8}{7}A=1-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{17}+\dfrac{1}{17}-\dfrac{1}{25}+...+\dfrac{1}{81}-\dfrac{1}{89}\)

\(\dfrac{8}{7}A=1-\dfrac{1}{89}=\dfrac{88}{89}\Rightarrow A=\dfrac{88}{89}:\dfrac{8}{7}=\dfrac{77}{89}\)

\(B=\dfrac{5^2}{1.4}+\dfrac{3^2}{4.7}+\dfrac{3^2}{7.10}+...+\dfrac{3^2}{37.40}\)

\(B=\dfrac{25}{1.4}+\dfrac{9}{4.7}+\dfrac{9}{7.10}+...+\dfrac{9}{37.40}\)

\(\dfrac{1}{3}B=\dfrac{25}{12}+\dfrac{3}{4.7}+\dfrac{3}{7.10}+...+\dfrac{3}{37.40}\)

\(\dfrac{1}{3}B=\dfrac{25}{12}+\dfrac{1}{4}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{10}+...+\dfrac{1}{37}-\dfrac{1}{40}\)

\(\dfrac{1}{3}B=\dfrac{25}{12}+\dfrac{1}{4}-\dfrac{1}{40}=\dfrac{277}{120}\Rightarrow B=\dfrac{277}{120}:\dfrac{1}{3}=\dfrac{277}{40}\)

\(A=\dfrac{7}{1.9}+\dfrac{7}{9.17}+\dfrac{7}{17.25}+...+\dfrac{7}{81.89}\)

\(=7\left(\dfrac{8}{1.9}+\dfrac{8}{9.17}+\dfrac{8}{17.25}+...+\dfrac{8}{81.89}\right)\)

\(=7\left(1-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{17}+\dfrac{1}{17}-\dfrac{1}{25}+\dfrac{1}{25}+...+\dfrac{1}{81}-\dfrac{1}{89}\right)\)

\(=7.\left(1-\dfrac{1}{89}\right)=7.\dfrac{88}{89}=\dfrac{616}{89}\)