Overall Review 2
𝑥=
7𝑦+9
𝑦+7

xy + 7x = 7y + 9  xy - 7y = -7x + 9
y(x-7) = -7x + 9 then divide by x-7
Domain of f(x) x≠7
Range of f(x) y≠ -7
Domain of f -1(x) x≠ -7
Range of f -1(x) y≠7
3x3 – x2 – 75x + 25 = 0
x2 (3x-1) -25(3x-1)
(x2 – 25)(3x-1)=0
(x-5)(x+5)(3x-1)=0
x = 1/3, -5,5
grouping
𝑥=𝑢
u2 + u – 20 = 0
(u+5)(u-4)=0
u = -5, 4
Find rate (k) first: ln0.5 =
e5600k
𝑘=
𝑙𝑛0.5
5600
𝑥=4
x = 16
. 74 = 𝑒
ln.74 =
𝑙𝑛0.5
( 5600 )𝑡
𝑙𝑛0.5
5600
5600∙𝑙𝑛0.74
𝑙𝑛0.5
𝑡
*multiply by reciprocal
= 𝑡  2433
82+82+85+87+𝑥
5
≥ 70
336 + 𝑥 ≥ 350
x  14
82+82+85+87+2𝑥
6
≥ 70
336 + 2𝑥 ≥ 420
x  42