Tìm x biết: (x – 5)(x – 4) – (x + 1)(x – 2) = 7
Giải thích
(x – 5)(x – 4) – (x+1)(x – 2) = 7
⇔ x2 – 4x – 5x + 20 – (x2 – 2x + x – 2) = 7
⇔ x2 – 4x – 5x + 20 – x2 + 2x – x + 2 = 7
⇔– 8x + 22 = 7
⇔– 8x = 7 – 22
⇔– 8x = – 15
⇔x=−15−8
⇔x=158
Vậy x=158.
(x – 5)(x – 4) – (x+1)(x – 2) = 7
⇔ x2 – 4x – 5x + 20 – (x2 – 2x + x – 2) = 7
⇔ x2 – 4x – 5x + 20 – x2 + 2x – x + 2 = 7
⇔– 8x + 22 = 7
⇔– 8x = 7 – 22
⇔– 8x = – 15
⇔x=−15−8
⇔x=158
Vậy x=158.