Eliminate y's
multiply second equaiton by 4
4x+4y=-4
add to first equation
3x-4y=-24
<u>4x+4y=-4 +</u>
7x+0y=-28
7x=-28
divide both sides by 7
x=-4
sub back
x+y=-1
-4+y=-1
add 4 to both sides
y=3
(x,y)
(-4,3)
D is answer
I'll go thru the problem and then you fill in the blanks yourself.
8 2
________
6 / 4 9 2
- 4 8
-----------------
1 2
1 2
--------------
0
80 - 2p
You use the distributive property
Alright, so after a half-life, half of the previous number would be left. So basically,
180 g ← 0 half lives
90 g ← 1 half life
45 g ← 2 half lives
22.5 g ← 3 half lives
11.25 g ← 4 half lives
Therefore, the answer is 11.25 grams
