\(5+\frac{96}{x^2-16}=\frac{2x-1}{x+4}+\frac{3x-1}{x-4}\)ĐKXĐ : \(x\ne\pm4\)

\(\Leftrightarrow\frac{5\left(x^2-16\right)}{x^2-16}+\frac{96}{x^2-16}=\frac{\left(2x-1\right)\left(x-4\right)}{x^2-16}+\frac{\left(3x-1\right)\left(x+4\right)}{x^2-16}\)

\(\Leftrightarrow5x^2-80+96=2x^2-9x+4+3x^2+11x-4\)

\(\Leftrightarrow5x^2-2x^2-3x^2-11x+9x=4-4+80-96\)

\(\Leftrightarrow-2x=-16\)

\(\Leftrightarrow x=8\)( t/m )

Vậy....

\(\frac{x}{40}+\frac{x}{35}=7,5\)

\(\Rightarrow x\cdot35+x\cdot40=7,5\)

\(\Rightarrow x\cdot(35+40)=7,5\)

\(\Rightarrow x\cdot75=7,5\)

\(\Rightarrow x=0,1\)

P/S : Hoq chắc :>

Ta có : \(\frac{x}{40}+\frac{x}{35}=7,5\)

\(\Rightarrow\frac{35x}{1400}+\frac{40x}{1400}=\frac{15}{2}\)

\(\Rightarrow\frac{75x}{1400}=\frac{15}{2}\)

\(\Rightarrow\frac{3x}{56}=\frac{420}{56}\)

\(\Rightarrow3x=420\)

\(\Rightarrow x=420:3=140\)

Vậy x = 140

hướng dẫn cách làm-tự làm tiếp nha :)

a) đặt \(k=x^2-4x\), ta có:\(k^2-2k=15\)\(\Rightarrow k^2-2x+1=16\Rightarrow\left(k-1\right)^2=4^2=\left(-4\right)^2\)

b) đặt \(A=x^2-3x\), ta có: \(A^2-2A-8=0\Rightarrow A^2-2A+1=9\Rightarrow\left(A-1\right)^2=3^2=\left(-3\right)^2\)

c)theo đề \(\Leftrightarrow\orbr{\begin{cases}x^2-4x+3=0\\x^2-8x+9=0\end{cases}}\)

\(x^2-4x+3=0\Leftrightarrow x^2-4x+4=1\Leftrightarrow\left(x-2\right)^2=1^2=\left(-1\right)^2\)

\(x^2-8x+9=0\Leftrightarrow x^2-8x+16=7\Leftrightarrow\left(x-4\right)^2=\pm\sqrt{7}^2\)

vt ko chi tiết bn ib là đc rùi, sai tớ làm gì T.T 

mà tớ làm mẫu 1 bài thui nha, bài còn lại có cách làm òi. bn tự dựa vô nha

\(\text{Đặt }k=x^2-4x,\text{ta có:}\)

\(\left(x^2-4x\right)^2-2.\left(x^2-4x\right)=15\)

\(\Leftrightarrow k^2-2k=0\)

\(\Leftrightarrow k^2-2k+1=16\)

\(\Leftrightarrow\left(k-1\right)^2=16\)

\(\Leftrightarrow\orbr{\begin{cases}k-1=4\\k-1=-4\end{cases}\Leftrightarrow\orbr{\begin{cases}k=5\\k=-3\end{cases}}}\)

\(\text{Với }k=5,\text{Ta có: }x^2-4x=5\Rightarrow x^2-4x-5=0\Rightarrow x^2-5x+x-5=0\)

\(\Rightarrow x.\left(x-5\right)+\left(x-5\right)=0\Rightarrow\left(x+1\right).\left(x-5\right)=0\Rightarrow\orbr{\begin{cases}x=-1\\x=5\end{cases}}\)

\(\text{Với }k=-3,\text{ta có: }x^2-4x=-3\Rightarrow x^2-4x+3=0\Rightarrow k^2-3x-x+3=0\)

\(\Rightarrow x.\left(x-3\right)-\left(x-3\right)=0\Rightarrow\left(x-1\right).\left(x-3\right)=0\Rightarrow\orbr{\begin{cases}x=1\\x=3\end{cases}}\)

Vậy...

a) \(6x^2-x-2=0\)

\(\Leftrightarrow6x^2-4x+3x-2=0\)

\(\Leftrightarrow2x\left(3x-2\right)+\left(3x-2\right)=0\)

\(\Leftrightarrow\left(3x-2\right)\left(2x+1\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}3x-2=0\\2x+1=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{2}{3}\\x=\frac{-1}{2}\end{cases}}\)

Vậy....

b) Ko có đề

c) Ko có đề

đề có đâu mà làm hả?

\(a^2+b^2+c^2=\left(a+b+c\right)^2\)

\(\Leftrightarrow a^2+b^2+c^2+2ab+2ac+2bc=a^2+b^2+c^2\)

\(\Leftrightarrow2\left(ab+ac+bc\right)=0\)

\(\Leftrightarrow ab+ac+bc=0\)

\(\Leftrightarrow\hept{\begin{cases}ab=-ac-bc\\ac=-ab-bc\\bc=-ab-ac\end{cases}}\)

Ta có : \(a^2+2bc=a^2+bc+bc=a^2+bc-ab-ac=a\left(a-b\right)-c\left(a-b\right)=\left(a-b\right)\left(a-c\right)\)

CMTT ta có : \(\hept{\begin{cases}b^2+2ac=\left(b-a\right)\left(b-c\right)\\c^2+2ab=\left(c-a\right)\left(c-b\right)\end{cases}}\)

Thay vào A ta được :

\(A=\frac{1}{\left(a-b\right)\left(a-c\right)}+\frac{1}{\left(b-a\right)\left(b-c\right)}+\frac{1}{\left(c-a\right)\left(c-b\right)}\)

\(A=\frac{b-c}{\left(a-b\right)\left(a-c\right)\left(b-c\right)}+\frac{-a+c}{\left(a-b\right)\left(a-c\right)\left(b-c\right)}+\frac{a-b}{\left(a-b\right)\left(a-c\right)\left(b-c\right)}\)

\(A=\frac{b-c-a+c+a-b}{\left(a-b\right)\left(a-c\right)\left(b-c\right)}\)

\(A=\frac{0}{\left(a-b\right)\left(a-c\right)\left(b-c\right)}\)

\(A=0\)

1. He got down to writing the letter as soon as he returned
=> No sooner had he returned from his walk than he got down to writing the letter.

2. She just had time to put up her umbrella before the rain came down in torrents
=> No sooner had she put up her umbrella than the rain came down in torrents.

3. The only way to eliminate world terrorism is by united opposition.
=> Only by united opposition can the world terrorism be eliminated.

4. The workers only called off the strike after a new pay offer.
=> Not until a new pay was offered did the workers call off the strike.

5. You are the best friend I can find in this world.
=> Nowhere in this world can I find a friend as good as you.

6. There was no precedent for the King's resignation.
=> .Never before had any King resigned.

7. I write to him almost everyday.
=> Hardly does a day go by without my writing to him.

8. Children can learn a lot about how to behave in a situation this.
=> Only in a situation this can children learn a lot about how to behave

9. You will find so many happy people nowhere else.
=> Nowhere else will you find so many happy people.

10. It's seldom wise to disregard the advice that he gives.
=> Seldom is it wise to disregard the advice that he gives

11. They have invited us to their home not once.
=> Not once have they invited us to their home.