Can someone help I don’t understand this!?
2 answers:
Answer:
A
Step-by-step explanation:
Let's label what we currently have:
Since the answer choices are asking us to use cosine, we will need to use the cosine formula:
It seems like we don't have the adjacent side yet. However, if we use another angle, we can find out what x is. We know one angle is 35°. Since it is a right triangle, the other angle is 90°. Since all triangles add up to 180°, we know that the other angle is 55°. We CAN use cosine to find x if we use the 55° angle.
Let's label our new areas:
By using the cosine formula, we can now use the two values we have in the equation.
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-2x+14 is the same as 14 - 2x
Let's say you started off with $14. If you want to buy a soda worth $2, then you have 14-2 = 12 dollars left. If you buy two sodas, then you spend 2*2 = 4 dollars with 14-4 = 10 dollars left.
In general, buying x sodas will cost you 2*x dollars and you have 14 - 2x dollars left over. The x is simply a placeholder for a whole number. For example, if x = 3, then...
14 - 2x = 14 - 2*3 = 14 - 6 = 8
meaning buying 3 sodas cost you $6 and you have $8 left over.
If y is the amount left over, then we can say y = 14 - 2x which is equivalent to y = -2x+14
note: graphing this equation will go through the two points (0,14) and (7,0) as shown in the image below. A graph is handy to help see various points on the line. Each point represents the amount of sodas you can buy (x) and the amount left over in your pocket (y). Keep in mind that neither x nor y can be negative, so it only makes sense to restrict the graph.
Alrighty
remember
means 
and
and
for all real values of x
so
means
means
which simplifies to
1=x²+4x-5
minus 1 both sides
0=x²+4x-6
use quadratic formula or complete the square
and 
2 solutions
remember
and
and
so
1=x²+4x-5
minus 1 both sides
0=x²+4x-6
use quadratic formula or complete the square
2 solutions