Math help!

1.
f(x) = Ca^x ...... (1)

Put x = 0 and f(x) = 3 into (1) :
Ca^0 = 3
C = 3

Put C = 3, x = 2 and f(x) = 12 into (1) :
3a^2 = 12
a^2 = 4
(a^2) - 4 = 0
(a - 2)(a + 2) = 0
a = 2 or a = -2


2.
6x + 4y = -4
4y = -6x - 4
2y = -(3x + 2)
y = -(3x + 2)/2

Hence,
x = x
y = -(3x + 2)/2

2011-09-30 13:45:24 補充：
第 2 題：If the system has infinitely many solutions, express your answer in the form x = x and y as a function of x.

第 2 題題目的意思是：若果 system (指 equation system) 有無限個 solutions (第 2 題便是這個情況) ，則把答案寫成 x = x，y 寫成 function of x。