a) 4x + 5(x - 3) = 3

<=> 4x + 5x - 15 = 3

<=> 9x = 3 + 15

<=> 9x = 18

<=> x = 2

   b) -3(x - 5) + 6(x + 2) = 9

<=> -3x + 15 + 6x + 12 = 9

<=> 3x + 27 = 9

<=> 3x = -18

<=> x = -6

\(\text{a, 3(x+1)+4x=10}\)

\(\Rightarrow3x+3+4x=10\)

\(\Rightarrow7x+3=10\)

\(\Rightarrow7x=10-3=7\)

\(\Rightarrow x=1\)

c, x+1/10+x+2/9=x+3/8+x+4/7

=> (x+1/10 +1) +(x+2/9 +1)= ( x+3/8 +1) +(x+4/7 +1)

=> x+11/10 + x+11/9 = x+11/8 + x+11/7

...............

a) \(3\left(x+1\right)+4x=10\)

\(\Rightarrow3x+3+4x=10\)

\(\Rightarrow3x+4x=10-3\)

\(\Rightarrow7x=7\)

\(\Rightarrow x=7\)

$x-3)2=9$

⇒[2x−3=32x−3=−3⇒[x=3x=0⇒[2x−3=32x−3=−3⇒[x=3x=0

Vậy x = 3 hoặc x = 0

\(\left(2x-3\right)^2=9\)

\(\left(2x-3\right)^2=3^2\)

⇒\(2x-3=+-3\)

\(TH1:2x-3=3\text{⇒}x=3\)

\(TH2:2x-3=-3\text{⇒}x=0\)

ta có: \(\left(2x-3\right)^2\)=\(3^2\)

2x-3=3

2x=3+3

2x=6

x=6:2

x=3

vậy x==3

Ta có: \(\left(x-3\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+9\left(x+1\right)^2=15\)

\(\Leftrightarrow x^3-9x^2+27x-27-x^3+27+9\left(x^2+2x+1\right)=15\)

\(\Leftrightarrow-9x^2+27x+9x^2+18x+9=15\)

\(\Leftrightarrow45x=6\)

hay \(x=\dfrac{2}{15}\)

\(a,\left(3x+x\right)\left(x^2-9\right)-\left(x-3\right)\left(x^2+3x+9\right)\)

\(=4x\left(x^2-9\right)-x^3+27\)

\(=4x^3-36x-x^3+27\)

\(=3x^3-36x+27\)

\(\left(x+6\right)^2-2x.\left(x+6\right)+\left(x-6\right).\left(x+6\right)\)

\(=\left(x+6\right).\left(x+6-2x+x-6\right)\)

\(=\left(x+6\right).0\)

\(=0\)

Mình làm phần tiếp của bạn Phạm Tuấn Đạt nha .

b) \(\left(x+6\right)^2-2x\left(x+6\right)+\left(x-6\right)\left(x+6\right)\)

\(=x^2+12x+36-2x^2-12x+x^2-36\)

\(=0\)

2. 

\(\left(2x-1\right)^2-\left(4x+1\right)\left(x-3\right)=-3\)

\(4x^2-4x+1-\left(4x^2-12x+x-3\right)=-3\)

\(4x^2-4x+1-4x^2+12x-x+3+3=0\)

\(7x+7=0\)

\(x=-1\)