Tìm x
a/ (x-5)(x+5)-(x+3)(x-1)(x+1)-(2x-3)=(x+1)-(x-4)(x+4)+3x2
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26 tháng 7 2021
1) Ta có: \(5\left(x-3\right)\left(x-7\right)-\left(5x+1\right)\left(x-2\right)=-8\)
\(\Leftrightarrow5\left(x^2-10x+21\right)-\left(5x^2-10x+x-2\right)=-8\)
\(\Leftrightarrow5x^2-50x+105-5x^2+9x+2+8=0\)
\(\Leftrightarrow-41x=-115\)
hay \(x=\dfrac{115}{41}\)
2) Ta có: \(x\left(x+1\right)\left(x+2\right)-\left(x+4\right)\left(3x-5\right)=84-5x\)
\(\Leftrightarrow x\left(x^2+3x+2\right)-\left(3x^2+7x-20\right)=84-5x\)
\(\Leftrightarrow x^3+3x^2+2x-3x^2-7x+20-84+5x=0\)
\(\Leftrightarrow x^3=64\)
hay x=4
3) Ta có: \(\left(9x^2-5\right)\left(x+3\right)-3x^2\left(3x+9\right)=\left(x-5\right)\left(x+4\right)-x\left(x-11\right)\)
\(\Leftrightarrow9x^3+27x^2-5x-15-9x^3-27x^2=x^2-x-20-x^2+11x\)
\(\Leftrightarrow-5x-15=10x-20\)
\(\Leftrightarrow-5x-10x=-20+15\)
\(\Leftrightarrow x=\dfrac{-5}{-15}=\dfrac{1}{3}\)
18 tháng 12 2021
Bài 1:
\(a,=6x^2+6x\\ b,=15x^3-10x^2+5x\\ c,=6x^3+12x^2\\ d,=15x^4+20x^3-5x^2\\ e,=2x^2+3x-2x-3=2x^2+x-3\\ f,=3x^2-5x+6x-10=3x^2+x-10\)
Bài 2:
\(a,\Leftrightarrow3x^2+3x-3x^2=6\\ \Leftrightarrow3x=6\Leftrightarrow x=2\\ b,\Leftrightarrow6x^2+3x-6x^2+9x-2x-3=10\\ \Leftrightarrow10x=13\Leftrightarrow x=\dfrac{13}{10}\)
4 tháng 1 2022
Bài 1:
a: \(=6x^3-10x^2+6x\)
b: \(=-2x^3-10x^2-6x\)
Bài 4:
a: =>3x+10-2x=0
=>x=-10
c: =>3x2-3x2+6x=36
=>6x=36
hay x=6
4 tháng 1 2022
Bài 1:
\(a,=6x^3-10x^2+6x\\ b,=-2x^3-10x^2-6x\)
Bài 4:
\(a,\Leftrightarrow3x+10-2x=0\Leftrightarrow x=-10\\ b,\Leftrightarrow x\left(2x^2+9x-5\right)-\left(2x^3+9x^2+x+4,5\right)=3,5\\ \Leftrightarrow2x^3+9x^2-5x-2x^3-9x^2-x-4,5=3,5\\ \Leftrightarrow-6x=8\Leftrightarrow x=-\dfrac{4}{3}\\ c,\Leftrightarrow3x^2-3x^2+6x=36\Leftrightarrow x=6\)
Bài 1:
\(a,=7xy\left(2x-3y+4xy\right)\\ b,=x\left(x+y\right)-5\left(x+y\right)=\left(x-5\right)\left(x+y\right)\\ c,=\left(x-y\right)\left(10x+8\right)=2\left(5x+4\right)\left(x-y\right)\\ d,=\left(3x+1-x-1\right)\left(3x+1+x+1\right)\\ =2x\left(4x+2\right)=4x\left(2x+1\right)\\ e,=5\left[\left(x-y\right)^2-4z^2\right]=5\left(x-y-2z\right)\left(x-y+2z\right)\\ f,=x^2+8x-x-8=\left(x+8\right)\left(x-1\right)\\ g,\left(x+y\right)^3-\left(x+y\right)=\left(x+y\right)\left[\left(x+y\right)^2-1\right]\\ =\left(x+y\right)\left(x+y-1\right)\left(x+y+1\right)\\ h,=x^2+3x+x+3=\left(x+3\right)\left(x+1\right)\)
3 tháng 2 2021
1/ 3-2x+4+6x=x+7+3x
⇔-2x+6x-x-3x=0
⇔0x=0 (Vô số nghiệm)
2/-6(1,5-2x)=3(-15+2x)
⇔-9+12x=-45+6x
⇔6x+36=0
⇔6(x+6)=0
⇔x+6=0
⇔x=-6
Vậy S ϵ {-6}
3/ 3(2x-5)+5(x-1)=4(x+1)
⇔6x-15+5x-5=4x+4
⇔7x=24
⇔x=\(\dfrac{24}{7}\)
Vậy S ϵ {\(\dfrac{24}{7}\)}
3 tháng 2 2021
1) Ta có: \(3-2x+4+6x=x+7+3x\)
\(\Leftrightarrow4x+7=4x+7\)
\(\Leftrightarrow4x+7-4x-7=0\)
\(\Leftrightarrow0x=0\)(luôn đúng)
Vậy: S={x|\(x\in R\)}
2) Ta có: \(-6\cdot\left(1.5-2x\right)=3\left(-15+2x\right)\)
\(\Leftrightarrow-9+12x=-45+6x\)
\(\Leftrightarrow12x-9+45-6x=0\)
\(\Leftrightarrow6x+36=0\)
\(\Leftrightarrow6x=-36\)
hay x=-6
Vậy: S={-6}
3) Ta có: \(3\left(2x-5\right)+5\left(x-1\right)=4\left(x+1\right)\)
\(\Leftrightarrow6x-15+5x-5=4x+4\)
\(\Leftrightarrow11x-20-4x-4=0\)
\(\Leftrightarrow7x-24=0\)
\(\Leftrightarrow7x=24\)
\(\Leftrightarrow x=\dfrac{24}{7}\)
Vậy: \(S=\left\{\dfrac{24}{7}\right\}\)
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AH
Akai Haruma
Giáo viên
10 tháng 8 2023
Lời giải:
$(x-5)(x+5)-(x+3)^2+3(x-2)^2=(x+1)^2-(x-4)(x+4)+3x^2$
$\Leftrightarrow x^2-25-(x^2+6x+9)+3(x^2-4x+4)=(x^2+2x+1)-(x^2-16)+3x^2$
$\Leftrightarrow 3x^2-18x-22=3x^2+2x+17$
$\Leftrightarrow -18x-22=2x+17$
$\Leftrightarrow 20x=-39$
$\Leftrightarrow x=\frac{-39}{20}$
