Question

13) -12( x - 5 ) + 7( 3 - x ) = 5

14) ( x - 2 ) . ( x + 4 ) = 0

15) ( x - 2 ) . ( x + 15 ) = 0

16) ( 7 - x ) . ( x + 19 ) = 0

17 ) -5 < x < 1

18) \(\left|x\right|\) < 3

19) ( x - 3 ) ( x - 5 ) < 0

20) 2x² - 3 = 29

Answer 1

14) (x - 2) . (x + 4) = 0

\(\Rightarrow\) x - 2 = 0 hoặc x + 4 = 0

Nếu x - 2 = 0

x = 0 + 2

x = 2

Nếu x + 4 = 0

x = 0 - 4

x = -4

Vậy x \(\in\) {2 ; -4)

Answer 2

15) (x - 2) . (x + 15) = 0

\(\Rightarrow\) x - 2 = 0 hoặc x + 15 = 0

Nếu x - 2 = 0

x = 0 + 2

x = 2

Nếu x + 15 = 0

x = 0 - 15

x = -15

Vậy x \(\in\) {-15 ; 2}

Answer 3

16) (7 - x) . (x + 19) = 0

\(\Rightarrow\) 7 - x = 0 hoặc x + 19 = 0

Nếu 7 - x = 0

x = 7 - 0

x = 7

Nếu x + 19 = 0

x = 0 - 19

x = -19

Vậy x \(\in\) {7 ; -19}

Answer 4

18) |x| < 3

Vì |x| \(\ge\) 0 với mọi x \(\in\) Z

|x| < 3

\(\Rightarrow\) |x| \(\in\) {2 ; 1 ; 0}

\(\Rightarrow\) x \(\in\) {-2 ; -1 ; 0 ; 1 ; 2}

Vậy x \(\in\) {-2 ; -1 ; 0 ; 1 ; 2}

Answer 5

2x² - 3 = 29

2x² = 29 + 3

2x² = 32

x² = 32 : 2

x² = 16

Vì 4² = (-4)² = 16

\(\Rightarrow\) x \(\in\) {4 ; -4}

Vậy x \(\in\) {4 ; -4}