11. a) 2x 3 x 1 x 2 x 2b) x2 – 4x ≤ 5 ⇔ (x – 2)2 ≤ 33 ⇔ | x – 2 | ≤ 3 ⇔ -3 ≤ x – 2 ≤ 3 ⇔ -1 ≤ x ≤ 5.c) 2x(2x – 1) ≤ 2x – 1 ⇔ (2x – 1)2 ≤ 0. Nhưng (2x – 1)2 ≥ 0, nên chỉ cĩ thể : 2x – 1 = 0Vậy : x = ½ .

A) 2X 3 X 1 X 2 X 2B) X2 – 4X ≤ 5 ⇔ (X – 2)2 ≤ 33 ⇔ | X – 2 | ≤ 3...

GIÁN ÁN 270 BAI TAP BD HSG CO DAP AN

11. a)

2x 3 x 1

x 2

b) x

– 4x ≤ 5 ⇔ (x – 2)

≤ 3

⇔ | x – 2 | ≤ 3 ⇔ -3 ≤ x – 2 ≤ 3 ⇔ -1 ≤ x ≤ 5.

c) 2x(2x – 1) ≤ 2x – 1 ⇔ (2x – 1)

≤ 0. Nhưng (2x – 1)

≥ 0, nên chỉ cĩ thể : 2x – 1 = 0

Vậy : x = ½ .