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a) 3 x a + 17 x b+ 14 x a - 170

= 3 x a + 14 x a + 17 x b - 170

= 17 x a + 17 x b - 170

= 17 x ( a+b) - 170

thay a + b = 100 vào, có:

17 x 100 - 170

= 1700 -170

= 1530

phần b thì mk ko bk, sr bn nha!

a) 3 x a + 17 x b+ 14 x a - 170

= 3 x a + 14 x a + 17 x b - 170

= 17 x a + 17 x b - 170

= 17 x ( a+b) - 170

thay a + b = 100 vào, có:

17 x 100 - 170

= 1700 -170

= 1530

a) 3 x a + 17 x b + 14 x a - 170 = a x (3 + 14) + 17 x b - 170

                                              = a x 17 + 17 x b - 170

                                              = 17 x (a + b) - 170

                                              = 17 x 100 - 170

                                              = 1700 - 170 

                                              = 1530

b) a x b + b x b + 12 x a + 199 = b x (a + b) + 12 x a + 199

                                             = b x 12 + 12 x a + 199

                                             = 12 x (b + a) + 199

                                             = 12 x 12 +199

                                             = 144 + 199

                                             = 343

Chúc bạn hok tốt nha!

= ax²- bx² + b - bx + bx² + bx - ax² - ax

= b - ax

`a)`

`A(x) + B(x) = 2x - 4x^2 + 1 + x^3 - 4x^2 + 5 - 2x`

                  `= x^3 - ( 4x^2 + 4x^2 ) + ( 2x - 2x ) + ( 1+ 5 )`

                  `= x^3 - 8x^2 + 6`

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`b)`

    `P(x) + B(x) = A(x)`

`=>P(x) = A(x) - B(x)`

`=>P(x) = 2x - 4x^2 + 1 + x^3 + 4x^2 - 5 + 2x`

`=>P(x) = x^3 + ( -4x^2 + 4x^2 ) + ( 2x + 2x ) + ( 1 - 5 )`

`=>P(x) = x^3 + 4x - 4`

b) \(B=\left(\dfrac{a\sqrt{a}+b\sqrt{b}}{\sqrt{a}+\sqrt{b}}\right):\left(a-b\right)+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\)

\(B=\left[\dfrac{\left(\sqrt{a}\right)^3+\left(\sqrt{b}\right)^3}{\sqrt{a}+\sqrt{b}}\right]:\left(a-b\right)+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\)

\(B=\left[\dfrac{\left(\sqrt{a}+\sqrt{b}\right)\left(a-\sqrt{ab}+\sqrt{b}\right)}{\sqrt{a}+\sqrt{b}}\right]:\left(a-b\right)+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\)

\(B=\left(a-\sqrt{ab}+\sqrt{b}\right):\left(a-b\right)+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\)

\(B=\dfrac{a-\sqrt{ab}+b}{a-b}+\dfrac{2\sqrt{b}\left(\sqrt{a}-\sqrt{b}\right)}{\left(\sqrt{a}+\sqrt{b}\right)\left(\sqrt{a}-\sqrt{b}\right)}\)

\(B=\dfrac{a-\sqrt{ab}+b}{a-b}+\dfrac{2\sqrt{ab}-2b}{a-b}\)

\(B=\dfrac{a-\sqrt{ab}+b+2\sqrt{ab}-2b}{a-b}\)

\(B=\dfrac{a+\sqrt{ab}-b}{a-b}\)

a) \(\sqrt{2}A=\sqrt{2x-2\sqrt{x-2}.\sqrt{x+2}}+\sqrt{2x+2\sqrt{x-2}.\sqrt{x+2}}\) (\(x\ge2\) )

\(=\sqrt{\left(x+2\right)-2\sqrt{x+2}.\sqrt{x-2}+\left(x-2\right)}+\sqrt{\left(x+2\right)+2\sqrt{x+2}.\sqrt{x-2}+\left(x-2\right)}\)

\(=\sqrt{\left(\sqrt{x+2}-\sqrt{x-2}\right)^2}+\sqrt{\left(\sqrt{x+2}+\sqrt{x-2}\right)^2}\)

\(=\left|\sqrt{x+2}-\sqrt{x-2}\right|+\sqrt{x+2}+\sqrt{x-2}\)

\(=\sqrt{x+2}-\sqrt{x-2}+\sqrt{x+2}+\sqrt{x-2}\) ( do \(x+2>x-2\ge0\Leftrightarrow\sqrt{x+2}>\sqrt{x-2}\) )

\(=2\sqrt{x+2}\)

\(\Leftrightarrow A=\sqrt{2}.\sqrt{x+2}\)

Vậy...

b) \(B=\left(\dfrac{a\sqrt{a}+b\sqrt{b}}{\sqrt{a}+\sqrt{b}}\right):\left(a-b\right)+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\) 

\(=\dfrac{\left(\sqrt{a}+\sqrt{b}\right)\left(a-\sqrt{ab}+b\right)}{\sqrt{a}+\sqrt{b}}.\dfrac{1}{a-b}+\dfrac{2\sqrt{b}}{\sqrt{a}+\sqrt{b}}\)

\(=\dfrac{a-\sqrt{ab}+b}{\left(\sqrt{a}-\sqrt{b}\right)\left(\sqrt{a}+\sqrt{b}\right)}+\dfrac{2\sqrt{b}\left(\sqrt{a}-\sqrt{b}\right)}{\left(\sqrt{a}+\sqrt{b}\right)\left(\sqrt{a}-\sqrt{b}\right)}\)

\(=\dfrac{a-\sqrt{ab}+b+2\sqrt{ab}-2b}{\left(\sqrt{a}+\sqrt{b}\right)\left(\sqrt{a}-\sqrt{b}\right)}\)

\(=\dfrac{a+\sqrt{ab}-b}{a-b}\)

Vậy...

\(VP=x^2+\left(a+b\right)x+ab=x^2+\text{ax}+bx+ab=x\left(a+x\right)+b\left(a+x\right)=\left(x+a\right)\left(x+b\right)=VT\left(\text{đ}pcm\right)\)

Cm ve phai

=x^2+<a+b>*x+ab

=(x^2+x)[(a+b)+(a+b)

=x(x+1).ab

\(\dfrac{1}{2}x=\dfrac{5}{8}-\dfrac{3}{4}\)

\(\dfrac{1}{2}x=-\dfrac{1}{8}\)

x=-1/8:1/2

x=-1/4

\(\dfrac{3}{4}+\dfrac{1}{2}x=\dfrac{5}{8}\)

\(\Leftrightarrow\dfrac{6}{8}+\dfrac{4x}{8}=\dfrac{5}{8}\)

\(\Leftrightarrow\dfrac{4x}{8}=\dfrac{5}{8}-\dfrac{6}{8}\)

\(\Leftrightarrow\dfrac{4x}{8}=-\dfrac{1}{8}\)

\(25\%\cdot x+x=-1.25\)

\(\Leftrightarrow0.25\cdot x+x=-1.25\)

\(\Leftrightarrow1.25x=-1.25\)

\(\Leftrightarrow x=-1\)

\(\Leftrightarrow x=-\dfrac{1}{4}\)

Giải:

a) \(\dfrac{3}{4}+\dfrac{1}{2}x=\dfrac{5}{8}\) 

           \(\dfrac{1}{2}x=\dfrac{5}{8}-\dfrac{3}{4}\) 

           \(\dfrac{1}{2}x=\dfrac{-1}{8}\) 

              \(x=\dfrac{-1}{8}:\dfrac{1}{2}\) 

             \(x=\dfrac{-1}{4}\) 

b) \(25\%x+x=-1,25\) 

\(x.\left(25\%+1\right)=-1,25\) 

         \(x.1,25=-1,25\) 

                 \(x=-1,25:1,25\) 

                 \(x=1\)

vào câu hỏi tương tự khác có

 Ta có:\(VT=\left(x+a\right)\left(x+5\right)\)

\(=x^2+\left(a+5\right)x+5a\)

Và \(VP=x^2+3x+b\)

Đồng nhất 2 vế ta có: \(\hept{\begin{cases}a+5=3\\b=5a\end{cases}}\Leftrightarrow\hept{\begin{cases}a=-2\\b=-10\end{cases}}\)