\(\left(3-x\right)\left(3+x\right)+\left(x-5\right)^2\\ =9-x^2+x^2-10x+25\\ =34-10x\)

Đặt x²+10x+5=a.Ta có biểu thức là : a(a+8)+16=a²+8a+16=(a+4)²=(x²+10x+9)²

đặt t= x² +10x+20 ta có phương trình <=> (t-4)(t+4)+16=0

                                                        <=> t²-16+16=0 

                                                        <=> t=0 
                                                        <=>x² +10x+20=0

giải nghiệm ra ta được x=-5+ căn 5 và x= -5- căn 5 

mấy bạn chi mk ý kiến nha .thanks

\(do:x=9\Rightarrow x+1=10\Rightarrow A=x^{16}-\left(x+1\right)x^{15}+\left(x+1\right)x^{14}-....+\left(x+1\right)=x^{16}-x^{16}-x^{15}+x^{15}+x^{14}-x^{14}-x^{13}+x^{13}+.....-x+x+1=1\)

\(-x^2+3x-4=-x^2+3x-2,25-1,75=-\left(x-\frac{3}{2}\right)^2-1,75< 0\left(đpcm\right)\)

Bài làm

\(B=\frac{16-\left(x+1\right)^2}{x^2+10x+25}\)

\(B=\frac{\left(4-x-1\right)\left(4+x+1\right)}{\left(x+5\right)^2}\)

\(B=\frac{\left(3-x\right)\left(x+5\right)}{\left(x+5\right)^2}\)

\(B=\frac{3-x}{x+5}\)

# Học tốt #

\(đk:x^2+2x+2\ne0\Leftrightarrow x^2+2x+1+1=\left(x+1\right)^2+1\ne0\left(luôn-đúng\right)\)

\(A=\dfrac{x^2+10x+16}{x^2+2x+2}\Leftrightarrow A\left(x^2+2x+2\right)=x^2+10x+16\)

\(\Leftrightarrow Ax^2+2Ax+2A-x^2-10x-16=0\)

\(\Leftrightarrow x^2\left(A-1\right)+x\left(2A-10\right)+2A-16=0\)

\(\Rightarrow\Delta\ge0\Leftrightarrow\left(2A-10\right)^2-4\left(A-1\right)\left(2A-16\right)\ge0\)

\(\Leftrightarrow4A^2-40A+100-4\left(2A^2-18A+16\right)\ge0\)

\(\Leftrightarrow-4A^2+32A+36\ge0\Rightarrow-1\le A\le9\Rightarrow\left\{{}\begin{matrix}MinA=-1\\MaxA=9\end{matrix}\right.\)

\(tại\) \(MinA=-1\) \(dấu"="\) \(xảy\) \(ra\Leftrightarrow x=-3\)

\(tại\) \(MaxA=9\) \(dấu"='\) \(xảy\) \(ra\Leftrightarrow x=-0,5\)

`1,(4x^3+3x^3):x^3+(15x^2+6x):(-3x)=0`

`<=> 4 + 3 + (-5x) + (-2)=0`

`<=> -5x+5=0`

`<=>-5x=-5`

`<=>x=1`

`2,(25x^2-10x):5x +3(x-2)=4`

`<=> 5x - 2 + 3x-6=4`

`<=> 8x -8=4`

`<=> 8x=12`

`<=>x=12/8`

`<=>x=3/2`

`3,(3x+1)^2-(2x+1/2)^2=0`

`<=> [(3x+1)-(2x+1/2)][(3x+1)+(2x+1/2)]=0`

`<=>( 3x+1-2x-1/2)(3x+1+2x+1/2)=0`

`<=>( x+1/2) (5x+3/2)=0`

`@ TH1`

`x+1/2=0`

`<=>x=0-1/2`

`<=>x=-1/2`

` @TH2`

`5x+3/2=0`

`<=> 5x=-3/2`

`<=>x=-3/2 : 5`

`<=>x=-15/2`

`4, x^2+8x+16=0`

`<=>(x+4)^2=0`

`<=>x+4=0`

`<=>x=-4`

`5, 25-10x+x^2=0`

`<=> (5-x)^2=0`

`<=>5-x=0`

`<=>x=5`

\(=x^2+2x+8x+16\)

\(=x\cdot\left(x+2\right)+8\cdot\left(x+2\right)\)

\(=\left(x+2\right)\cdot\left(x+8\right)\)