S1 Maths Help

Simplify 2x-5x^2+5-x^2+3x-1
2x-5x^2+5-x^2+3x-1
=2x+3x-5x^2-x^2+5-1
=5x-6x^2+4

equations 1. 9-3a-16=5a+9
9-3a-16=5a+9
9-3a=5a+9+16
9-3a=5a+25
9=5a+3a+25
9=8a+25
9-25=8a
-16=8a
a=-2

equations 2. 50-2(5k+4)=-4(3k-7)
50-2(5k+4)=-4(3k-7)
50-10k-8=-12k-(-28)
42-10k=-12k+28
42-10k+12k=28
42+2k=28
2k=-14
k=-7

Simplify
2x - 5x^2 + 5 - x^2 + 3x - 1
= 5x - 6x^2 + 4
= - ( 6x^2 - 5x - 4)
= - ( 3x - 4 ) ( 2x + 1 )

equation
1) 9 - 3a - 16 = 5a + 9
9 - 16 - 9 = 5a + 3a
- 16 = 8a
8a = -16
a = -2

2) 50 - 2 ( 5k + 4 ) = - 4 ( 3k - 7 )
50 - 10k - 8 = - 12k + 28
50 - 8 - 28 = - 12k + 10k
14 = - 2k
2k = -14
k = -7

Simplify 2x-5x^2+5-x^2+3x-1

= -5x^2x^2 +2x+3x +5-1
= -4x^2 +5x +4

Equation
1. 9-3a-16=5a+9

put all the 'a' to one side and the integers to another.

5a+3a = 9-16-9
8a = -16
a= -2

2. 50-2(5k+4)=-4(3k-7)

expand the brackets first
-2(5k+4) = -10k-8
-4(3k-7) = -12k+28

50-10k-8= -12k + 28

put all the 'k' to one side and integers to another

-10k+12k = 28+8-50
2k = -14
k = -7

2012-11-09 23:26:00 補充：
Simplify :
2x-5x^2+5-x^2+3x-1

=-5x^2-x^2+2x+3x+5-1
= -6x^2+5x+4

*unable to factorize.