b) 3^2x = 81

    3^2x = 3⁴

=> 2x = 4

=>   x = 2

a). 5^2x-3 – 2.5² = 5² .3 

             5^2x: 5³ = 5² .3 + 2.5² 

             5^2x: 5³ = 5² .5

                   5^2x = 5² .5.5³ 

                   5^2x = 5⁶

               => 2x = 6

                  => x=3

a). 5^x = 125

=>5^x = 5³

=> x = 3

b) 3^2x = 81

=> 3^2x = 3⁴

=> 2x = 4

=> x = 2

c). 5^2x-3 – 2.5² = 5² .3

=>5^2x: 5³ = 5² .3 + 2.5²

=>5^2x: 5³ = 5² .5

=>
5^2x = 5² .5.5³

=>5^2x = 5⁶

=> 2x = 6

=> x=3

a) 5x = 125

x = 125 : 5

x = 25

b) 32x = 81

x = 81 : 32

x = 81/ 32

c) 52x - 3 - 2.52 = 52.3

52x - 3 - 104 = 156

x - 3 - 104 = 156 : 52

x - 3 - 104 = 3

x - 3 = 3 + 104

x - 3 = 107

x = 107 + 3

x = 110

Ko chắc lắm , sai thì Sorry nhé .

\(a,\\ 5x=125\\ < =>x=125:5\\ < =>x=25\)

\(b,\\ 32x=81\\ < =>x=81:32\\ < =>x=\frac{81}{32}\)

\(c,\\ 52x-3-2.52=52.3\\ < =>52x-3-104=156\\ < =>52x-107=156\\ < =>52x=156+107\\ < =>52x=263\\ < =>x=x=\frac{263}{52}\)

a) \(6x^2-75x-81=0\)

Vì \(a-b+c=6-\left(-75\right)+81=0\)

Vậy: \(x_1=-1;x_2=\dfrac{-\left(-81\right)}{6}=\dfrac{27}{2}\)

b) \(5x^2-32x+27=0\)

Vì \(a+b+b=5+\left(-32\right)+27=0\)

Vậy: \(x_1=1;x_2=\dfrac{27}{5}\).

Chọn D

Đáp án D

a: \(\left(2x-3\right)\left(3x^2+1\right)-6x\left(x^2-x+1\right)+3x^2-2x=10\)

\(\Leftrightarrow6x^3+2x-9x^2-3-6x^3+6x^2-6x+3x^2-2x=10\)

\(\Leftrightarrow-6x-3=10\)

=>-6x=13

hay x=-13/6

b: \(\Leftrightarrow3x^2-3x+x-2-3x^2+5x=-8-5x\)

=>3x-2=-5x-8

=>8x=-6

hay x=-3/4

c: \(\Leftrightarrow64x^3-27-64x^3+32x^2-32x^2+x=20\)

=>x-27=20

hay x=47

x = 4

\(3x\sqrt{2x}-3\sqrt{2x}+2\sqrt{2x}\)

\(2\sqrt{2x}\)

3√2x−√18x+12√32x

=\(3\sqrt{2x}-3\sqrt{2x}+48\sqrt{2x}\)

=\(48\sqrt{2x}\)

\(=3\sqrt{2x}-3\sqrt{2x}+\dfrac{1}{2}\cdot4\sqrt{2x}\)

\(=2\sqrt{2x}\)