Tìm số nguyên x biết

a) 15x + 25 = 100

b) \(42 - \left[ {5x - \left( { - 32} \right)} \right] + 12:2 = 6\)

 

a)

\(\begin{array}{l}15x + 25 = 100\\15x\,\,\,\,\,\,\,\,\,\,\, = 100 - 25\\15x\,\,\,\,\,\,\,\,\,\,\, = 75\\\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\, = 75:15\\\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\, = 5\end{array}\)

Vậy x = 5.

b) 

\(\begin{array}{l}42 - \left[ {5x - \left( { - 32} \right)} \right] + 12:2 = 6\\42 - \left( {5x + 32} \right) + 6 = 6\\42 - \left( {5x + 32} \right)\,\,\,\,\,\,\,\,\, = 6 - 6\\42 - \left( {5x + 32} \right)\,\,\,\,\,\,\,\,\, = 0\\\,\,\,\,\,\,\,\,\,\,\,\,5x + 32\,\,\,\,\,\,\,\,\,\,\, = 42 - 0\\\,\,\,\,\,\,\,\,\,\,\,\,5x + 32\,\,\,\,\,\,\,\,\,\,\, = 42\\\,\,\,\,\,\,\,\,\,\,\,\,5x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 42 - 32\\\,\,\,\,\,\,\,\,\,\,\,\,5x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 10\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 10:5\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,x\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 2\end{array}\)

Vậy x = 2.