Question

[Ánh Vũ Ngọc]

1, Tìm x biết:

a, x\(^2\) - 2x +1 = 0

b, ( 5x + 1)\(^2\) - (5x - 3) ( 5x + 3) = 30

c, ( x - 1) ( x\(^2\) + x + 1) - x ( x +2 ) ( x - 2) = 5

d, ( x - 2)\(^3\) - ( x - 3) ( x\(^2\) + 3x + 9 ) + 6 ( x + 1)\(^2\) = 15

2, Chứng minh các đa thức sau luôn luôn dương với mọi x, y :

a, x\(^2\) + 2x + 2

b, 4x\(^2\) - 12x + 11

c, x\(^2\) - x + 1

d, x\(^2\) - 2x + y\(^2\) + 4y + 6

3, Tìm x, y biết :

a, x\(^2\) + y\(^2\) - 2x + 4y + 5 = 0

b, x\(^2\) + 4y\(^2\) + 6x - 12y + 18 = 0

c, 5x\(^2\) + 9y\(^2\) - 12xy - 6x + 9 = 0

d, 2x\(^2\) + 2y\(^2\) + 2xy - 10x - 8y + 41 = 0

Answer 1

[L.A Bibi Trần]

1.

a. x² - 2x + 1 = 0

x² - 2x*1 + 1² = 0

(x-1)² = 0

............( tới đây tui bí rùi tự suy nghĩ rùi lm tiếp ik)

Answer 2

[-๖ۣۜGiả๖ۣۜTạo๖ۣۜ]

1, Tìm x biết:

a, x - 2x +1 = 0

(x-1)² = 0

x-1 = 0

x = 1. Vậy ...

b, ( 5x + 1) - (5x - 3) ( 5x + 3) = 30

25x² +10x + 1 - (25x² -9) = 30

25x² +10x + 1 - 25x² +9 = 30

10x + 10 =30

10(x+1) = 30

x+1 =3

x = 2. vậy ...

c, ( x - 1) ( x + x + 1) - x ( x +2 ) ( x - 2) = 5

(x³ - 1) - x(x² -4) = 5

x³ - 1 - x³ + 4x = 5

4x - 1 = 5

4x = 6

x = \(\dfrac{3}{2}\) .vậy ...

d, ( x - 2) - ( x - 3) ( x + 3x + 9 ) + 6 ( x + 1) = 15

x³ - 6x² + 12x - 8 - (x³ - 27) + 6 (x² + 2x +1) =15

x³ - 6x² + 12x - 8 - x³ + 27 + 6x² + 12x +6 =15

24x + 25 = 15

24x = -10

x = \(\dfrac{-5}{12}\) vậy ...