Rút gọn biểu thức :
\(3x\left(x-5\right)-5x\left(x+7\right)\)
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24 tháng 8 2018
\(5x^2-3x\left(x-2\right)\)
\(=5x^2-3x^2+6x\)
\(=2x^2+6x\)
\(-4x^2+2x-4x\left(x-5\right)\)
\(=-4x^2+2x-4x^2+20x\)
\(=-8x^2+22x\)
\(3x\left(x-5\right)-5x\left(x+7\right)\)
\(=3x^2-15x-5x^2+35x\)
\(=-2x^2+20x\)
5 tháng 6 2019
\(M=\frac{-2x}{3}+3x\left(\frac{x}{6}-\frac{-2}{9}-\frac{7}{5}\right)-\frac{5x}{2}\left(\frac{x}{5}-\frac{4}{5}\right)\)
\(M=\frac{-2x}{3}+3x\left(\frac{x}{6}+\frac{2}{9}-\frac{7}{5}\right)-\frac{5x}{2}.\frac{x-4}{5}\)
\(M=\frac{-2x}{3}+3x\left(\frac{15x+20-126}{90}\right)-\frac{5x^2-20x}{10}\)
\(M=\frac{-2x}{3}+3x.\frac{15x-106}{90}-\frac{5.\left(x^2-4x\right)}{10}\)
\(M=\frac{-2x}{3}+\frac{45x^2-318x}{90}-\frac{x^2-4x}{2}\)
H9
HT.Phong (9A5)
CTVHS
22 tháng 6 2023
\(A=3x\left(x-4y\right)-\dfrac{12}{5}y\left(y-5x\right)\)
\(A=3x^2-12xy-\dfrac{12}{5}y^2+12xy\)
\(A=3x^2-\dfrac{12}{5}y^2\)
Thay \(x=4;y=-5\) vào A ta được:
\(3\cdot4^2-\dfrac{12}{5}\cdot\left(-5\right)^2=48-60=-12\)
Vậy ....
5 tháng 10 2021
\(\left(5-3x\right)\left(5+3x\right)-\left(x+1\right)^3\)
\(=25-9x^2-x^3-3x^2-3x-1\)
\(=-x^3-12x^2-3x+24\)
29 tháng 3 2023
7:
a: =>0,5x-5=2 hoặc 0,5x-5=-2
=>0,5x=3 hoặc 0,5x=7
=>x=6 hoặc x=14
b: |5x-2|=-3
mà |5x-2|>=0
nên ptvn
c: =>1/4x+3=0
=>1/4x=-3
=>x=-12
15 tháng 11 2023
ĐKXĐ: \(x\notin\left\{0;-5\right\}\)
\(A=\dfrac{x^2}{5x+25}+\dfrac{2\left(x-5\right)}{x}+\dfrac{50+5x}{x\left(x+5\right)}\)
\(=\dfrac{x^2}{5\left(x+5\right)}+\dfrac{2\left(x-5\right)}{x}+\dfrac{5x+50}{x\left(x+5\right)}\)
\(=\dfrac{x^3+2\cdot5\left(x-5\right)\left(x+5\right)+5\left(5x+50\right)}{5x\left(x+5\right)}\)
\(=\dfrac{x^3+10x^2-250+25x+250}{5x\left(x+5\right)}\)
\(=\dfrac{x^3+10x^2+25x}{5x\left(x+5\right)}=\dfrac{x\left(x^2+10x+25\right)}{5x\left(x+5\right)}\)
\(=\dfrac{\left(x+5\right)^2}{5\left(x+5\right)}=\dfrac{x+5}{5}\)
15 tháng 11 2023
\(A=\dfrac{x^2}{5x+25}+\dfrac{2\left(x-5\right)}{x}+\dfrac{50+5x}{x\left(x+5\right)}\left(ĐKXĐ:x\ne0;x\ne-5\right)\)
\(A=\dfrac{x^2}{5\left(x+5\right)}+\dfrac{2\left(x-5\right)}{x}+\dfrac{50+5x}{x\left(x+5\right)}\)
\(A=\dfrac{x^2.x}{5x\left(x+5\right)}+\dfrac{2.5\left(x+5\right)\left(x-5\right)}{5x\left(x+5\right)}+\dfrac{5\left(50+5x\right)}{5x\left(x+5\right)}\)
\(A=\dfrac{x^3}{5x\left(x+5\right)}+\dfrac{10.\left(x^2-25\right)}{5x\left(x+5\right)}+\dfrac{250+25x}{5x\left(x+5\right)}\)
\(A=\dfrac{x^3}{5x\left(x+5\right)}+\dfrac{10x^2-250}{5x\left(x+5\right)}+\dfrac{250+25x}{5x\left(x+5\right)}\)
\(A=\dfrac{x^3+10x^2-250+250+25x}{5x\left(x+5\right)}\)
\(A=\dfrac{x^3+10x^2+25x}{5x\left(x+5\right)}\)
\(A=\dfrac{x\left(x^2+10x+25\right)}{5x\left(x+5\right)}\)
\(A=\dfrac{\left(x+5\right)^2}{5\left(x+5\right)}\)
\(A=\dfrac{x+5}{5}\)
2 tháng 10 2021
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: \(\left(3a+1\right)^2+2\left(9a^2-1\right)+\left(3a-1\right)^2\)
\(=\left(3a+1+3a-1\right)^2\)
\(=36a^2\)
5 tháng 10 2021
\(\left(3x-5\right)^2+\left(x+2\right)^2+x\left(3-4x\right)\)
\(=9x^2-30x+25+x^2+4x+4+3x-4x^2\)
\(=6x^2-23x+29\)
\(=\left(3x^2-15x\right)-\left(5x^2+35x\right)\)
\(=3x^2-15x-5x^2-35x\)
\(=3x^2-5x^2-15x-35x\)
\(=-2x^2-50x\)
ủng hộ nha
\(3x\left(x-5\right)-5x\left(x+7\right)\)
\(=3x^2-15x-5x^2-35x\)
\(=-2x^2-50x\)