Nguyễn Khắc Vinh như vậy nghĩa là gì?

Ta có : $(-113-39)+(239-400)-100-287$

$=-113-39+239-400-100-287$

$=-(113+287)+(239-39)-(400+100)$

$=-400+200-500=-700$

Bài này có mũ 200 hay 200 hay 20000 thì nó cũng chẳng ảnh hưởng gì nhé =))

Ta có : $(3x-\dfrac{1}{5})^{200})+(\dfrac{2}{5}y+\dfrac{4}{7})^1968=0$

Vì $3x-\dfrac{1}{5})^{200}\geq 0$

$\dfrac{2}{5}y+\dfrac{4}{7}^1968\geq 0$

\(=>\left\{{}\begin{matrix}\left(3x-\dfrac{1}{5}\right)^{200}=0\\\left(\dfrac{2}{5}y+\dfrac{4}{7}\right)^{1968}=0\end{matrix}\right.\)

\(=>\left\{{}\begin{matrix}\left(3x-\dfrac{1}{5}\right)=0\\\left(\dfrac{2}{5}y+\dfrac{4}{7}\right)^{ }=0\end{matrix}\right.\)

\(=>\left\{{}\begin{matrix}3x=\dfrac{1}{5}\\\dfrac{2}{5}y=\dfrac{-4}{7}\end{matrix}\right.\)

\(=>\left\{{}\begin{matrix}x=\dfrac{1}{15}\\y=\dfrac{-10}{7}\end{matrix}\right.\)

Ta có : $2^{-5n}=\dfrac{1}{2^{5n}}$

$5^{-2n}=\dfrac{1}{5^{2n}}$

Lúc này ta chỉ cần so sánh $2^{5n}$ và $5^{2n}$

$2^{5n}=(2^5)^n=32^n$

$5^{2n}=(5^2)^n=25^n$

Vì $32^n>25^n$

$=>2^{5n}>5^{2n}$

$=>\dfrac{1}{2^{5n}}>\dfrac{1}{5^{2n}}$

$=>2^{-5n}<5^{-2n}$ (đổi dấu)

1. a) $(5-2x)^2-16=0$

$=>(5-2x)^2-4^2=0$

$=>(5-2x-4)(5-2x+4)=0$

$=>(1-2x)(9-2x)=0$

\(=>\left[{}\begin{matrix}1-2x=0=>x=0,5\\9-2x=0=>x=4,5\end{matrix}\right.\)

b) $x^2-4x=29$

$=>x^2-4x-29=0$

$=>(x^2-4x+4)-33=0$

$=>(x-2)^2-(\sqrt{33})^2=0$

$=>(x-2-\sqrt{33})(x-2+\sqrt{33})=0$

\(=>\left[{}\begin{matrix}x-2-\sqrt{33}=0=>x=\sqrt{33}+2\\x-2+\sqrt{33}=0=>x=2-\sqrt{33}\end{matrix}\right.\)

hai tư là hư tai tick mình nhé !

a) $x^2+20x+100=x^2=2.10x+10^2=(x+10)^2$

b) $x^2-20xy+100y^2=x^2-2.x.10y+(10y)^2=(x+10y)^2$

c) $x^2-20x+100=x^2-2.10x+10^2=(x-10)^2$

a) Ta có : $M=|x+\dfrac{15}{19}|\geq 0$

Vậy MinM = 0 khi và chỉ khi $<=>x+\dfrac{15}{19}=0=>x=\dfrac{-15}{19}$.

b) Ta có : $|x-\dfrac{4}{7}|\geq 0$

$=>N=|x-\dfrac{4}{7}|-\dfrac{1}{2}\geq \dfrac{-1}{2}$

Vậy MinN = $\dfrac{-1}{2}$ khi và chỉ khi $<=>|x-\dfrac{4}{7}|=0=>x=\dfrac{4}{7}$

B = $(x+2)^3-(x-2)^3-12x^3$

$=>B=(x+2-x+2)[(x+2)^2+(x+2)(x-2)+(x-2)^2]-12x^3$

$=>B=4(x^2+4x+4+x^2-4+x^2-4x+4)-12x^3$

$=>B=4(3x^2+4)-12x^3$

$=>B=12x^2+16-12x^3$

$=>B=12x^2(1-x)+16$