d) 2(x+5) - x\(^2\) - 5x = 0
\(TH1:2\left(x+5\right)=0\)
\(\rightarrow2x+10=0\)
\(\rightarrow2x=-10\)
\(\rightarrow x=-5\)
\(TH2:-x^2=0\)
\(\rightarrow x=0\)
\(TH3:-5x=0\)
\(\rightarrow x=0\)
Tìm x, biết:
a) (x+1)\(^2\) - (x+1) = 0
\(\left(x+1\right)\left(x+1-1\right)=0\)
\(\left(x+1\right)\left(x+0\right)=0\)
\(\left(x+1\right).x=0\)
\(TH1:x+1=0\)
\(\rightarrow x=-1\)
\(TH2:x=0\)
c) (x+3)\(^2\) - (2x-1)\(^2\) = 0
\(\left[\left(x+3\right)-\left(2x-1\right)\right].\left[\left(x+3\right)+\left(2x-1\right)\right]=0\)
\(\left(x+3-2x+1\right).\left(x+3+2x-1\right)=0\)
\(\left(-x+4\right).\left(3x-2\right)=0\)
\(TH1:-x+4=0\)
\(\rightarrow-x=-4\)
\(\rightarrow x=4\)
\(TH2:3x-2=0\)
\(\rightarrow3x=2\)
\(\rightarrow x=\frac{2}{3}\)
