Tìm x thuộc ℕ biết: a) (x - 15) × 15 = 0 b) 32(x - 10) = 32 c) (x - 5)(x - 7) = 0 d) (x - 35) × 35 = 35

a) (x - 15) × 15 = 0

⇔ x – 15 = 0

⇔ x = 0 + 15

⇔ x = 15

b) 32(x - 10) = 32

⇔ x – 10 = 1

⇔ x = 1 + 10

⇔ x = 11

c) (x - 5)(x - 7) = 0

⇔ \(\left[ \begin{array}{l}x - 5 = 0\\x - 7 = 0\end{array} \right.\)

⇔ \(\left[ \begin{array}{l}x = 5\\x = 7\end{array} \right.\)

d) (x - 35) × 35 = 35

⇔ x – 35 = 1

⇔ x = 1 + 35

⇔ x = 36.