Question

giải cho mình bài tập nha 

 1, tính 

\(a,(\frac{-7}{3})^3\div(\frac{-7}{3})^2\)

\(b,(\frac{-4}{9})\div(\frac{-4}{9})^3\)

\(c,(\frac{1}{5})^{10}\div(\frac{1}{5})^7\)

2, tìm x

a,\(\frac{-x}{7}=\frac{1}{-21}\)

\(B,4\frac{2}{5}\cdot0,5-1\frac{3}{7}\)

\(c,3x^2-2x=0\)

\(d,9x^2-1=0\)

 

Answer 1

1. 

a) (—7/3)³:(—7/3)²=(—7/3)^3–2=—7/3

b) (—4/9):(—4/9)³= (—4/9)^1–3=(—4/9)^—2=81/16

c) (1/5)¹⁰:(1/5)⁷=(1/5)^10–7=(1/5)³=1/125

2. 

a) —x/7 =1/—21

==> —x.(—21)=7.1

==> —x.(—21)=7

==> —x=7:(—21)

==> —x=—1/3

==> x=1/3

b) 4 2/5 . 0,5–1 3/7= 22/5 . 1/2 —10/7= 22.1/5.2–10/7=  11/5 —10/7= 77/35 — 50/35= 27/35

c) 3x²–2x=0

==> x³(3–2)=0

x³.1=0

x³=0:1

x³=0

==> x=0

c) 9x²–1=0

9x²=0+1

9x²=1

x²=1:9

x²=1/9

x²=1²/3² hoặc x²=(—1/3)²

Vậy x=1/3 hoặc x=—1/3