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# 數學 代數

Factorise fully:

2x^2+11x+20

Solve:

3x+4y=13

4x-5y=38

x=?

y=?

Update:

Solve:

6(x+1)>2x+3

### 2 Answers

Rating

- 螞蟻雄兵Lv 710 years agoFavorite Answer
Factorise

fully:

1. 2x^2+11x+20

Sol

2x^2+11x+20

D=11^2－4*2*20=121－160=－39<0

在實係數下無法再因式分解

2. Solve

3x+4y=13

4x－5y=38

x=?

y=?

Sol

3x+4y=13--------(1)

4x－5y=38------(2)

5*(1)+4*(2)

5*(3x+4y)+4(4x－5y)=65+152

15x+16x=217

x=7---------------(3)代入(1)

3*7+4y=13

4y=－8

y=－2-----------(4)

3. Solve:

6(x+1)>2x+3

Sol

6x+6>2x+3

4x>－3

x>－3/4

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- AlexLv 510 years ago
2.

3x+4y=13.......(1)

4x-5y=38........(2)

(1)*5+(2)*4

31x=217

x=7

代入(1)

y= -2

Ans：x=7，y= -2

2010-04-27 15:46:39 補充：

3.

6(x+1)>2x+3

6x+6 > 2x+3

6x -2x > 3 -6

4x > -3

x > -3/4

2010-04-27 15:58:19 補充：

1.

2x^2+11x+20 無法完全因式分解

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