a/ -3x=-60+30
=> -3x=-30
=> x=(-30):(-3)
=> x=10
Ban oi phai x,y∈Z thi moi lam dc
b/x.y=7
Vi x,y∈U(7)=(1,-1,7,-7)
Với x=1 => y=7 y=1=>x=7
x=-1 =>x=-7 y=-1=>x=-7
x=7 => x=1 y=7=>x=7
x=-7 => x=-1 y=-7=>x=-1
c/(x-1)(y+2)=-7
x-1 va y+2∈U(-7)=(1,-1,7,-7)
Bạn giải giống câu b/ nhưng x,y trái đâu nhé
d/2x-3=5x-7
=>(-3)+7=5x-2x
=>4=3x
=>x=4/3
e/(-2)2-8x=20
=>4-8x=20
=>4-20=8x
=>-16=8x
=>x=-2
f/17-(-31)+3x=2x-(-50)
=>17+31+3x=2x+50
=>49+3x=2x+50
=> 3x-2x=50-49
=> x=1
g/2y2-16=34
=>2y2=34+16
=>2y2=50
=>y2=50:2
=>y2=25=52=(-5)2
=>y=5 va y=-5
a) \(\left(-3\right)x-30=-60\)
\(\Leftrightarrow\left(-3\right)x=-60+30\)
\(\Leftrightarrow\left(-3\right)x=-30\)
\(\Leftrightarrow x=\left(-30\right):\left(-3\right)\)
\(\Leftrightarrow x=10\)
b) \(xy=7\)
\(\Rightarrow xy=1.7=7.1=\left(-1\right).\left(-7\right)=\left(-7\right).\left(-1\right)\)
Ta có bảng sau:
| \(x\) | \(1\) | \(7\) | \(-1\) | \(-7\) |
| \(y\) | \(7\) | \(1\) | \(-7\) | \(-1\) |
KL: Các cặp số (x; y)...
c) \(\left(x-1\right)\left(y+2\right)=-5\)
\(\Rightarrow\left(x-1\right)\left(y+2\right)=1.\left(-5\right)=\left(-5\right).1=\left(-1\right).5=5.\left(-1\right)\)
Ta có bảng sau:
| \(x-1\) | \(1\) | \(-5\) | \(5\) | \(-1\) |
| \(y+2\) | \(-5\) | \(1\) | \(-1\) | \(5\) |
| \(x\) | \(2\) | \(-4\) | \(6\) | \(0\) |
| \(y\) | \(-7\) | \(-1\) | \(-3\) | \(3\) |
KL: Các cặp số (x; y)...
d) \(2x-3=5x-7\)
\(\Leftrightarrow2x-5x=-7+3\)
\(\Leftrightarrow-3x=-4\)
\(\Leftrightarrow x=\dfrac{4}{3}\)
e) \(\left(-2\right)^2-8x=20\)
\(\Leftrightarrow4-8x=20\)
\(\Leftrightarrow8x=4-20\)
\(\Leftrightarrow8x=-16\)
\(\Leftrightarrow x=-2\)
f) \(17-\left(-31\right)+3x=2x-\left(-50\right)\)
\(\Leftrightarrow17+31+3x=2x+50\)
\(\Leftrightarrow48+3x=2x+50\)
\(\Leftrightarrow3x-2x=50-48\)
\(\Leftrightarrow x=2\)
g) \(2y^2-16=34\)
\(\Leftrightarrow2y^2=34+16\)
\(\Leftrightarrow2y^2=50\)
\(\Leftrightarrow y^2=50:2=25\)
\(\Leftrightarrow y^2=5^2=\left(-5\right)^2\)
\(\Leftrightarrow\left[{}\begin{matrix}y=5\\y=-5\end{matrix}\right.\)
