2/3 x - 2/5   = 1/2 x - 1/3

2/3 x - 1/2 x = 2/5 - 1/3        ( chuyển vế đổi dấu )

( 2/3 - 1/2 ) x = 6/15 - 5/15

( 4/6 - 3/6 ) x = 1/15

       1/6       x = 1/15

                    x = 1/15 : 1/6

                    x = 1/15 x 6

                    x = 6/15

\(S=\left(-2,3\right)+\left(41,5\right)+\left(-0,7\right)+\left(-1,5\right)\)

\(=[\left(-2,3\right)+\left(-0,7\right)]+[\left(41,5\right)+\left(-1,5\right)]\)

\(=\left(-3\right)+40=37\)

Bài  1 :

a) Vì ( x + 1 )² ≥ 0 ∀ x

=> M = ( x + 1 )² - 3 ≥ -3

Dấu "=" xảy ra <=> ( x + 1 )² = 0

<=> x + 1 = 0 <=> x = -1

b) Vì ( y + 3 )² ≥ 0 ∀ x

=> N = 5 - ( y + 3 )² ≥ 5

Dấu "=" xảy ra <=> ( y + 3 )² = 0

<=> y  + 3 = 0 <=> y = -3

tim tim 

em thay x = 9y/8 vào x+ y+ z=49

3y/4- 4z/5 = 0..... như vậy là được 2 ẩn 2 phương trình

\(\frac{x^3}{16}=4\Rightarrow x^3=4.16\)

\(\Rightarrow x^3=64=4^3\)

=> x = 4

\(\frac{x^3}{16}=4=>x^3:16=4\)

\(x^3=64< =>4^3=64=>x=3\)

\(=\frac{2^{15}.3^8}{2^{12}.2^9}=\frac{3^8}{2^6}=3^8:2^6=81^2:8^2=\left(\frac{81}{8}\right)^2\)

\(\frac{2^{15}.9^4}{6^6.8^3}=\frac{2^{15}.\left(3^2\right)^4}{\left(2.3\right)^6.\left(2^3\right)^3}=\frac{2^{15}.3^8}{2^6.3^6.2^9}=\frac{2^{15}.3^8}{2^{15}.3^6}=3^2=9\)