ร20-21

-1/2 51 x3 − 3x2  10x

x3 − 3x2  10x

x3 − 3x2 −10x  0

( )x x2 − 3x −10  0

x(x − 5)(x + 2)  0

x = 0 , x = 5 x = −2

-3 -2 -1 0 1 2 3 4 5 6

x3 − 3x2  10x (− ,−2 0,5

x x  −2 0  x  5  = (− ,−2 0,5

2 2x3 − 5x2 − 4x + 3  0
-1/2 5

2x3 − 5x2 − 4x + 3 = (2x −1)(x +1)(x − 3)

(2x −1)(x +1)(x − 3)  0

x = 1 , x = −1 x=3

2

-1 1/2 3

2x3 − 5x2 − 4x + 3  0 (− ,−1  1 ,3
 2

 x x  −1 1  x 3  = (− ,−1 1 ,3
 2   2
 

3 (x + 2)(x + 4)3  0

(x + 2)(x + 4)3  0

(x + 2)(x + 4)2 (x + 4)  0

(x + 4)2  0 x x  R − − 4

(x + 4)2

(x + 2)(x + 4)  0 x  −4

x = −2 , x = −4

-4 -2

x x  −4 x  −2  = (− ,−4) (− 2, )



4 21
x−3 x+2

21 -+ -+
x−3 x+2
2 − 1 0
x−3 x+2

2 (x + 2) −(x − 3)  0 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
(x − 3) (x+ 2)

2x + 4 −x+3  0 x xx −x7 −7 − 2 −x2−x33= (−=(−,−7
− 2  x  3  = (− ,−7) (− 2,3)
(x − 3) (x + 2)

( x − x+ 7 + 2)x 0x  −7
x
3)(

(x − 3)2 (x + 2)2

(x − 3)(x + 2)(x + 7)  0 x  3 x  −2

x = 3 , x = −2 x = −7

5 ( x − 3)( x + 7)  0

x+2

( x − 3)( x + 7)  0

x+2

(x + 2)2

(x − 3()x(x−+32))((xx ++ 77)) 00 x  −2
x+2
x = −7
x = 3 , x = −2

-+ -+

-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7

x − 7  x  −2 x  3  = − 7,−2) 3, )

5

1. (x −1)(x + 2)(x − 3)  0

2. x3 − x  2x2 − 2
3. 5 − x  1

x2 − 3x + 2
4. x 2 + 6  5

x

a=2 b=3

1. a + 2b 2. 9 a 3. − a − 7(a − − a )

b