a) \(\left(2x+3\right)\left(x-4\right)+\left(x+5\right)\left(x-2\right)=\left(3x-5\right)\left(x-4\right)\)

\(\Leftrightarrow2x^2-8x+3x-12+x^2-2x-5x+10=3x^2-12x-5x+20\)

\(\Leftrightarrow2x^2-8x+3x-12+x^2-2x+10=3x^2-12x+20\)

\(\Leftrightarrow3x^2-7x-2=3x^2-12x+20\)

\(\Leftrightarrow-7x+12x=20+2\)

\(\Leftrightarrow5x=22\)

\(\Rightarrow x=\dfrac{22}{5}\)

tick cho mk nha

b) \(\left(8x-3\right)\left(3x+2\right)-\left(4x+7\right)\left(x+4\right)=\left(2x+1\right)\left(5x-1\right)\)

\(\Leftrightarrow24x^2+16x-9x-6-4x^2-23x-28=10x^2+3x-1\)

\(\Leftrightarrow20x^2-16x-34-10x^2-3x+1=0\)

\(\Leftrightarrow10x^2-19x-33=0\)

\(\Delta=\left(-19\right)^2-4.10.\left(-33\right)=1320\)

\(x_1=3;x_2=\dfrac{-11}{10}\)

Tick cho mk nha

c) \(\left(3x-5\right)\left(7-5x\right)-\left(5x+2\right)\left(2-3x\right)=4\)

\(\Leftrightarrow21x-15x^2-35+25x-4x+15x^2-4=4\)

\(\Leftrightarrow42x-39=4\)

\(\Leftrightarrow42x=4+39\)

\(\Leftrightarrow42x=43\)

\(\Rightarrow x=\dfrac{43}{42}\)

Tick cho mk nha

a/ \(x=\dfrac{-5}{12}\)

b/ \(x\approx-1,9526\)

c/ \(x=\dfrac{21-i\sqrt{199}}{10}\)

d/ \(x=\dfrac{-20}{13}\)

a) (x-2)³+6(x+1)²-x³+12=0

⇒ x³-6x²+12x-8+6(x²+2x+1)-x³+12=0

⇒ x³-6x²+12x-8+6x²+12x+6-x³+12=0

⇒ 24x+10=0

⇒ 24x=-10

⇒ x=-5/12

a.

PT \(\Leftrightarrow x^3-6x^2+12x-8+6(x^2+2x+1)-x^3+12=0\)

\(\Leftrightarrow x^3-6x^2+12x-8+6x^2+12x+6-x^3+12=0\)

\(\Leftrightarrow 24x+10=0\Leftrightarrow x=\frac{-5}{12}\)

b. Bạn xem lại đề, nghiệm khá xấu không phù hợp với mức độ tổng thể của bài.

c.

PT $\Leftrightarrow (4x^2+12x+9)+(x^2-1)=5(x^2+4x+4)+(x^2-4x-5)+9(x^2+6x+9)$
$\Leftrightarrow 10x^2+42x+64=0$

$\Leftrightarrow x^2+(3x+7)^2=-15< 0$ (vô lý) 

Do đó pt vô nghiệm.

d.

PT $\Leftrightarrow (1-6x+9x^2)-(9x^2-17x-2)=(9x^2-16)-9(x^2+6x+9)$

$\Leftrightarrow 11x+3=-54x-97$

$\Leftrightarrow 65x=-100$

$\Leftrightarrow x=\frac{-20}{13}$

MK ĐANG CẦN GẤP Ạ AI NHANH MK SẼ VOTE Ạ

a: Ta có: \(\left(3x-1\right)^2-2\left(5x-2\right)^2-2\left(x^2+x-1\right)\left(x-1\right)\)

\(=9x^2-6x+1-2\left(25x^2-20x+4\right)-2\left(x^3-x^2+x^2-x-x+1\right)\)

\(=9x^2-6x+1-50x^2+40x-8-2\left(x^3-2x+1\right)\)

\(=-41x^2+34x-7-2x^3+4x-2\)

\(=-2x^3-41x^2+38x-9\)

b: Ta có: \(\left(3a+1\right)^2+2\left(9a^2-1\right)+\left(3a-1\right)^2\)

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

\(=36a^2\)

em chưa cho đa thức f(x) và g(x) nà

a: \(\dfrac{f\left(x\right)}{g\left(x\right)}\)

\(=\dfrac{x^4-9x^3+21x^2+ax+b}{x^2-x-1}\)

\(=\dfrac{x^4-x^3-x^2-8x^3+8x^2+8x+14x^2-14x-14+\left(a+6\right)x+b+14}{x^2-x-1}\)

\(=x^2-8x+14+\dfrac{\left(a+6\right)x+b+14}{x^2-x-1}\)

Để f(x) chia hết cho g(x) thì a+6=0 và b+14=0

=>a=-6 và b=-14

b: \(\dfrac{f\left(x\right)}{g\left(x\right)}=\dfrac{x^4-x^3+5x^2+x^2-x+5+a-5}{x^2-x+5}\)

\(=x^2+1+\dfrac{a-5}{x^2-x+5}\)

Để f(x) chia hết g(x) thì a-5=0

=>a=5

Bạn xem lại đề nhé.

a) \(A=x^2+5y^2+2xy-4x-8y+2015\)

\(A=x^2-4x+4-2y\left(x-2\right)+y^2+2011+4y^2\)

\(A=\left(x-2\right)^2-2y\left(x-2\right)+y^2+2011+4y^2\)

\(A=\left(x-2-y\right)^2+4y^2+2011\)

Vì \(\left(x-y-2\right)^2\ge0;4y^2\ge0\)

\(\Rightarrow A_{min}=2011\)

Dấu bằng xảy ra : \(\Leftrightarrow\left\{{}\begin{matrix}x-y-2=0\\4y^2=0\end{matrix}\right.\Leftrightarrow}\left\{{}\begin{matrix}x=2\\y=0\end{matrix}\right.\)

b) \(B=\left(x-2012\right)^2+\left(x+2013\right)^2\)

\(B=x^2-4024x+2012^2+x^2+4026x+2013^2\)

\(B=2x^2+2x+2012^2+2013^2\)

\(B=2\left(x^2+x+\dfrac{1}{4}\right)+2012^2+2013^2-\dfrac{1}{2}\)

\(B=2\left(x+\dfrac{1}{2}\right)^2+2012^2+2013^2-\dfrac{1}{2}\)

\(\Rightarrow B_{min}=2012^2+2013^2-\dfrac{1}{2}\)

Dấu bằng xảy ra : \(\Leftrightarrow x=-\dfrac{1}{2}\)

a) (x-1)^x+2=(x-1)².(x-1)^x+2

=> (x-1)²=1

=> x-1=1

=>x=2

b) | 3x - 4 | + | 5y + 5 | = 0   

Ta có  \(\hept{\begin{cases}\left|3x-4\right|\ge0\\\left|5y+5\right|\ge0\end{cases}\forall xy}\)

\(\Leftrightarrow\left|3x-4\right|+\left|5y+5\right|\ge0\forall xy\)  

Do đó để tổng | 3x - 4 | + | 5y + 5 | = 0    thì \(\hept{\begin{cases}\left|3x-4\right|=0\\\left|5y+5\right|=0\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}3x-4=0\\5y+5=0\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}3x=4\\5y=-5\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}x=\frac{4}{3}\\y=-1\end{cases}}\)

Vậy \(x=\frac{4}{3}\) và y= - 1 

c) | x + 3 | + | x + 1 | = 3x  (*1)

Ta có \(\hept{\begin{cases}\left|x+3\right|\ge0\\\left|x+1\right|\ge0\end{cases}\forall x}\)

\(\Leftrightarrow\) | x + 3 | + | x + 1 | \(\ge0\forall\)x

\(\Leftrightarrow3x\ge0\forall x\)

\(\Leftrightarrow x\ge0\)

\(\Leftrightarrow x+3>x+1>x\ge0\)

\(\Leftrightarrow\hept{\begin{cases}\left|x+3\right|=x+3\\\left|x+1\right|=x+1\end{cases}}\)

\(\Leftrightarrow\left|x+3\right|+\left|x+1\right|=x+3+x+1\)

\(\Leftrightarrow\left|x+3\right|+\left|x+1\right|=2x+4\)  (*2)

Từ (*1) và (*2) <=> 2x + 4 = 3x

\(\Leftrightarrow4=3x-2x\)

\(\Leftrightarrow x=4\)

Vậy x = 4

Câu a t đang nghi sai đề

Lát t lm đc thì lm sau nhé

câu a t làm ra mà

sao ko ai thấy đúng v

b. (x²-0,5):2x-(3x-1)²:(3x-1)=0

<=> \(\frac{1}{2}\)x-0,25-3x+1=0

<=>\(-\frac{5}{2}\)x+0,75=0

<=> \(-\frac{5}{2}\)x=-0,75

<=> x=0,3

chúc bạn học tốt

\(a.\left(x+1\right)\left(x+2\right)\left(x+4\right)\left(x+5\right)=4\)

\(\Leftrightarrow\left[\left(x+1\right)\left(x+5\right)\right]\left[\left(x+2\right)\left(x+4\right)\right]=4\)

\(\Leftrightarrow\left(x^2+x+5x+5\right)\left(x^2+4x+2x+8\right)=4\)

\(\Leftrightarrow\left(x^2+6x+5\right)\left(x^2+6x+8\right)=4\)

\(\text{Đặt a = }x^2+6x+5\text{ }\Rightarrow\text{ }a+3=x^2+6x+8\)

\(\Leftrightarrow a\left(a+3\right)=4\)

\(\Leftrightarrow a^2+3a-4=0\)

\(\Leftrightarrow a^2+4a-a-4=0\)

\(\Leftrightarrow a\left(a+4\right)-\left(a+4\right)=0\)

\(\Leftrightarrow\left(a+4\right)\left(a-1\right)=0\)

\(\Leftrightarrow\left(x^2+6x+9\right)\left(x^2+6x+4\right)=0\)

\(\Leftrightarrow\left(x+3\right)^2\left[\left(x^2+6x+9\right)-5\right]=0\)

\(\Leftrightarrow\left(x+3\right)^2\left[\left(x+3\right)^2-5\right]=0\)

\(\text{Hoặc }\left(x+3\right)^2=0\Leftrightarrow x+3=0\Leftrightarrow x=-3\)

\(\text{Hoặc }\left(x+3\right)^2-5=0\Leftrightarrow\left(x+3\right)^2=5\Leftrightarrow\hept{\begin{cases}x+3=\sqrt{5}\\x+3=-\sqrt{5}\end{cases}\Leftrightarrow\hept{\begin{cases}x=\sqrt{5}-3\\x=-\sqrt{5}-3\end{cases}}}\)

\(\text{Vậy }x\in\left\{-3;\sqrt{5}-3;-\sqrt{5}-3\right\}\)

a: Ta có: \(\left(7x+4\right)^2-\left(7x-4\right)\left(7x+4\right)\)

\(=\left(7x+4\right)\left(7x+4-7x+4\right)\)

\(=8\left(7x+4\right)\)

=56x+32

b: Ta có: \(8\left(x-2\right)^2-3\left(x^2-4x-5\right)-5x^2\)

\(=8x^2-32x+32-3x^2+12x+15-5x^2\)

\(=-20x+47\)

c: Ta có: \(\left(x+1\right)^3-\left(x-1\right)\left(x^2+x+1\right)-3x\left(x+1\right)\)

\(=x^3+3x^2+3x+1-x^3+1-3x^2-3x\)

=2

Rảnh rỗi thật sự .-.

len google di ban

mk chua hoc bai nay