a)(x-4).(x-1)2=0 b)(2x-6).(x2+1)=0(bó tay)
x-(4.1)2=0 c)(bó tay)(làm được nhưng lười)
x-42=0
x-8=0
x=0+8
x+8
\(a,\left(x-4\right)\left(x-1\right)^2=0\)
\(\Rightarrow\orbr{\begin{cases}x-4=0\\\left(x-1\right)^2=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x-4=0\\x-1=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=4\\x=1\end{cases}}\)
\(b,\left(2x-6\right)\left(x^2+1\right)=0\)
Vì \(\left(x^2+1\right)\ge0vs\forall x\)
\(\Rightarrow\left(2x-6\right)\left(x^2+1\right)=0\Leftrightarrow2x-6=0\)
\(\Rightarrow2x=6\Rightarrow x=3\)
\(c,1+2+3+4+....+x=78\)
\(\Rightarrow x\left(x+1\right):2=78\)
\(\Rightarrow x\left(x+1\right)=78.2\)
\(\Rightarrow x\left(x+1\right)=156\)
\(\Rightarrow x\left(x+1\right)=12.13\)
\(\Rightarrow x=12\)
giups mình mai mình phải nộp bài gòi