中一英數[急](20點)

(1)Simplify:
(a)5x2-2x+4-2x2-x+10
=3x2-3x+14

(b)(x+4y-z)+(5x-4y+3z)
=x+4y-z+5x-4y+3z
=6x+2z

(c)(2h-k)-(5h-9k)
=2h-k-5h+9k
=8k-3h
(d)6(a+b)-4(a-b)
=6a+6b-4a+4b
=2a+10b
(2)In a factory , a worker tested(70+2x)radios. Of the tested radios, he found out that (x-37) radios did notmeet the production requirement. How many radios met the productionrequirement?
(70+2x) – (x-37)
= 70+2x – x+37
=103 + x
(103 + x) radiosmet the production requirement.
(3)A man buys n eggs at $3m each and sellsthem at $(n-5m) each. After he has sold all the eggs, how much did he gain?
[(n-5m)-3m] x n
=(n-8m) x n
=n2-8m
He gained $(n2-8m).

(4)Tommy is five years older than May, the sum of their ages is29.Find Tommy's age.
Let Tommy’sage be x years, May’s age be (x-5) years
x + ( x – 5 )= 29
2x-5=29
2x = 34
X 17
Tommy’s age is17.

(5)Johnny's weight is 8kg more than twice that of Kenny's, thesum of their weights is 158kg.Find Johnny's weight.
Let Johnny’s weightbe x Kg, Kenny’s weight be [(x – 8 )/2] Kg
x + [(x – 8 )/2]=158
x + x/2 – 4 = 158
x + x/2 = 162
2x + x = 324
3x = 324
x = 108
Johnny’sweight is 108 Kg.
(6)(1/2)x-7=5+x
- (1/2)x =12
x = 12 x (-2)
x = -24

(7)Find x if 400% of x is320
x * 400% = 320
x = 320 400%
x = 320 x 1/4
x = 80

1a) ?(I don't know what is 5x2, I'm sorry for cannot solve this question )

1b) (x 4y-z) (5x-4y 3z)
=x 4y-z 5x-4y 3z
=6x 2z

1c) (2h-k)-(5h-9k)
=2h-k-5h 9k
=-3h 8k

1d) 6(a b)-4(a-b)
=6a 6b-4a 4b
=2a 10b

2) (70 2x)-(x-37)
=70 2x-x 37
=107 x

3) (n-5m)-3m
=n-8m

4) Let's May's age be x, than Tommy's age be x 5
x x 5=29
2x 5=29
2x=24
x=12
Therefore, May's age is 12 years old, Tommy;s age is (12) 5=17 years old.

5) Let x be Kenny's weight
2x 8 x=158
3x 8=158
3x=150
x=50
Therefore Kenny's weight is 50kg, Johnny's weight is (50)*2 8=108kg

6) 1/2x-7=5 x
1/2x-x=5 7
x/2-2x/2=12
-x/2=12
-x=24
x=-24

7) 320/400%
=320/4
=80

Hope I can help you!!

2008-08-03 16:15:13 補充：
1a) 5x2-2x+4-2x2-x+10
=3x2-3x+14

2008-08-03 16:20:21 補充：
1d) 6(a+b)-4(a-b)
=6a+6b-4a+4b
=2a+10b

2) (70+2x)-(x-37)
=70+2x-x+37
=107-x

(1)Simplify:
(a)5x2-2x+4-2x2-x+10 = (5-2)x^2 +(-2-1)x +(4+10)
= 3x^2 - 3x + 16
(b)(x+4y-z)+(5x-4y+3z) = (5+1)x + (4-4)y + (-1+3)z
= 6x+2z


(c)(2h-k)-(5h-9k) = (2-5)h +(-1 +9)k
= -3h +8k

(d)6(a+b)-4(a-b) = (6-4)a + (6+4)b
= 2a +10b
(2)
radios met the production requirement = (70+2x) -(x-37)
= 107 + x
(3)
The buying egg charge = 3m(n) = $3mn
The selling egg amount = (n - 5) (n) = n^2 - 5n
The amount gains = n^2 - 5n - 3mn = n^2 - (5+3m)n
(4)
Let tommy's age be x
x-5 be May's age
x + (x-5) = 29
2x = 34
x = 17
Tommy's age is 17
(5)
Let Johnny's weight be 2x+8
Kenny's weight be x
2x+8 + x = 158
3x = 150
x = 50kg
Johnny's weight = 2x+8 = 2(50)+8 = 108kg
(6)
1/2x - 7 = 5+x
-12 = 1/2x
x = -24
(7)
400%x = 320
4x = 320
x = 80