a, \(x\) + 99: 3 = 55
\(x\) + 33 = 55
\(x\) = 55 - 33
\(x\) = 22
b, (\(x\) - 25):15 = 20
\(x\) - 25 = 20 x 15
\(x\) - 25 = 300
\(x\) = 300 + 25
\(x\) = 325
c, (3\(x\) - 15).7 = 42
3\(x\) - 15 = 42:7
3\(x\) - 15 = 6
3\(x\) = 6 + 15
3\(x\) = 21
\(x\) = 21: 3
\(x\) = 7
d, (8\(x\) - 16).(\(x\) -5) = 0
\(\left[{}\begin{matrix}8x-16=0\\x-5=0\end{matrix}\right.\)
\(\left[{}\begin{matrix}8x=16\\x=5\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=16:8\\x=5\end{matrix}\right.\)
\(\left[{}\begin{matrix}x=2\\x=5\end{matrix}\right.\)
Vậy \(x\) \(\in\) {2; 5}
e, \(x\).(\(x\) + 1) = 2 + 4 + 6 + 8 + 10 + ...+ 2500
\(x\).(\(x\) + 1) = 2.(1 + 2 + 3 +...+1250)
\(x\).(\(x\)+1) = 2. (1250+1).1250: 2
\(x\).(\(x\)+1) = 1250.(1250+1)
\(x\) = 1250
a) x + 99 : 3 = 55 b) ( x - 25 ) : 15 = 20
x = 55 - 33 x - 25 = 20.15
x = 22 x = 300 + 25
Vậy x = 22 x = 325
c) 7( 3x - 15 ) = 42 Vậy x = 325
3x - 15 = 42 : 7 d) ( 8x - 16 )( x - 5 ) = 0
3x = 6 + 15 TH1: 8x - 16 = 0
x = 21 : 3 8x = 0 + 16
x = 7 x = 16 : 8
Vậy x = 7 x = 2
TH2: x - 5 = 0
x = 0 + 5
x = 5
Vậy x ϵ \(\left\{2;5\right\}\)
a) x + 33 = 55 x = 55 - 33 x = 22
b) x- 25 = 20 x 15 x - 25 = 300 x = 300 + 25 x = 325
c)( 3.x - 15 ) = 42 /7 3. x - 15 = 6 x.3 =6 + 15 x . 3 = 21 x = 21/3 x = 7 d) :((
