x/5 = y/2 = z/-3 suy ra (x/5)^3 = ( y/2 )^3= (z/-3)^3 = x/125 = y/8 = z/-27 = xyz/5.2 .(-3) = 2/-30 = 1/-15 = -1/15.

=> x = -1; y = -2/15; z = 1/5.

KL:x = -1; y = -2/15; z = 1/5.

hm hơi khó đó

B1:\(a,\frac{7}{5}-\frac{11}{4}-\frac{5}{4}-\frac{3}{5}=\frac{6}{4}-\frac{4}{5}=\frac{3}{2}-\frac{4}{5}=\frac{15-8}{10}=\frac{7}{10}\)

\(b,=\frac{1}{3}.\frac{-4}{5}.\frac{1}{4}.\frac{12}{1}=-\frac{48}{60}=-\frac{4}{5}\)

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