ĐK: $x\ge -1$

$\sqrt{9x+9}+\sqrt{x+1}=20$

$\Leftrightarrow 3\sqrt{x+1}+\sqrt{x+1}=20$

$\Leftrightarrow 4\sqrt{x+1}=20$

$\Leftrightarrow \sqrt{x+1}=5$

$\Leftrightarrow x+1=25$

$\Leftrightarrow x=24(TM)$

Đua top trên Hoc24 có phải là điểm GP cao trên top không ạ ?

a/ Pt $\Leftrightarrow x^3+8-x^2+2x=15$

$\Leftrightarrow 2x=7\\\Leftrightarrow x=3,5$

b/ Pt $\Leftrightarrow x^3+27-x^2+3x=18$

$\Leftrightarrow 3x=-9\\\Leftrightarrow x=-3$

$\Leftrightarrow x-\dfrac{1}{2}=\dfrac{1}{2}\\\Leftrightarrow =1$

Use 'enough' with these words

Tina is very thin. She doesn't .... (eat)

a/ $\begin{cases}|2x-y|\ge 0\\|3x-6|\ge 0\end{cases}$

$\Rightarrow |2x-y|+|3x-6|\ge 0$

Dấu "=" xảy ra khi $2x-y=3x-6=0$

$\Leftrightarrow x=2;y=6$

b/ $\begin{cases}|2y-x|\ge 0\\(x-3)^2\ge 0\end{cases}$

$\Rightarrow |2y-x|+(x-3)^2\ge 0$

Dấu "=" xảy ra khi $2y-x=x-3=0$

$\Leftrightarrow x=3;y=1;5$

0,6km=600m

$t=\dfrac{s}{v}=\dfrac{600}{4}=150s$

a/ $=x^2(x^2+2x+1)-y^2\\=[x(x+1)]^2-y^2\\=[x(x+1)-y][x(x+1)+y]\\=(x^2+x-y)(x^2+x+y)$

b/ $=(x^3-8)+(x^2-2x)\\=(x-2)(x^2+2x+4)+x(x-2)\\=(x-2)(x^2+2x+5)$