Maths (要列式的) ....急用

1. (2a+1)(a-1)(3a+5)
= (2a^2+a-2a-1)(3a+5)
= (2a^2-a-1)(3a+5)
= 6a^3-3a^2-3a+10a^2-5a-5
= 6a^3+7a^2-8a-5

2. The possible range of weight is between 57.5 kg and 58.4 kg (58.5 kg will become 59 kg).

3. (2x+3)(x-2)
= 2x^2+3x-4x-6
= 2x^2-x-6
Therefore, (i) the coefficient of x is -1 and (ii) the constant term is -6.

1. Expend (2a+1)(a-1)(3a+5)

(2a+1)(a-1)(3a+5)
=(2a^2 - a - 1)(3a + 5)
=6a^3 - 3a^2 - 3a + 10a^2 - 5a - 5
=6a^3 + 7a^2 - 8a - 5

2. The weight of a student is measured to be 58 kg,correct to the nearest 0.5kg.Find the possible range of his weight.

Correct to the nearest 0.5kg
max. error = 0.5kg/2 = 0.25kg
lower limit = (58 - 0.25)kg = 57.75kg
upper limit = (58 + 0.25)kg = 58.25kg


Hence possible range of his weight is between 57.75kg to 58.25kg

3.(a) Expand(2x+3)(x-2)
(2x+3)(x-2)
= 2x^2 - 4x + 3x - 6
= 2x^2 - x - 6

(b) Hence,find (i) the coefficient of x ;

the coefficient of x = -1

(ii) the constant term

the constant term = -6

2006-10-29 00:04:02 補充：
第二題不服。
不是correct to the nearest 0.5kg.