a)(x+5)³-15x(x+10)

=x³+15x²+75x+125-15x²-150x

=x³+75x+125

b) (x-2)²-(x-5)²

=(x-2-x+5)(x-2+x-5)

=3.(2x-7)

=6x-21

c)(x+2)(x²-2x+4)-(x³+8)

=(x³+8)-(x³+8)

=0

#H

`C4:`

`x/[x-2]+2/[2-x]=x/[x-2]-2/[x-2]=[x-2]/[x-2]=1`

`C5:[15x^2]/[17y^4] . [34y^5]/[15x^3]`

 `=[15x^2 . 2.17y^4 . y]/[17y^4 . 15x^2 . x]=[2y]/x`

`C5:[6x+18]/[(x+4)^2]:[3(x+3)]/[x+4]`

 `=[6(x+3)]/[(x+4)^2] . [x+4]/[3(x+3)]`

`=2/[x+4]`

=15x²-(17x²-2x²-4x)

=15x²-15x²-4x

=4x

k cho mik nếu banh thấy đúng nhé!

1:

\(A=\sqrt{x^2+\dfrac{2x^2}{3}}=\sqrt{\dfrac{5x^2}{3}}=\left|\sqrt{\dfrac{5}{3}}x\right|=-x\sqrt{\dfrac{5}{3}}\)

2: \(=\left(\dfrac{\sqrt{100}+\sqrt{40}}{\sqrt{5}+\sqrt{2}}+\sqrt{6}\right)\cdot\dfrac{2\sqrt{5}-\sqrt{6}}{2}\)

\(=\dfrac{\left(2\sqrt{5}+\sqrt{6}\right)\left(2\sqrt{5}-\sqrt{6}\right)}{2}\)

\(=\dfrac{20-6}{2}=7\)

Chọn A

A

chon A bạn nhé

a. 2x

b.\({3x}\over x^2-1\)

1)10x-3x(x-5)+3(x²-4x)-3x

<=>3(x²-4x)+10x-3x-3x(x-5)

<=>3(x²-4x)=7x-3x(x-5)

<=>3x²-12x+7x-3x²+15x

<=>3x²-3x²-12x+7x+15x

<=>-12x+7x+15x

<=>10x

2)5^y+1-4.5^y

<=>5¹.5^y-4.5^y

<=>5^y(5¹-4)

<=>5^y.1

<=>5^y