The largest possible value of b is 10, since for some x = x₀ it could be the case that f(x₀) = -5 and g(x₀) = -2; then f(x₀) g(x₀) = -5 × -2 = 10.
Adding both equations cancels y:
<span>4x + 8y = 16
</span><span>4x - 8y = 0
-----------------+
8x = 16 => x=2
filling in x=2 in the first equation gives:
4*2 + 8y = 16 => 8y = 8 => y=1
So (2,1) is the (x,y) pair that solves the two equations. Answer C.</span>
Answer:
- The system of equations is x + y = 85 and 7/20x+2/5y=31
- To eliminate the x-variable from the equations, you can multiply the equation with the fractions by 20 and multiply the other equation by -7.
- B-She used 60 minutes for calling and 25 minutes for data.
Step-by-step explanation:
It is always a good idea to start by defining variables in such a problem. Here, we can let x represent the number of calling minutes, and y represent the number of data minutes. The the total number of minutes used is ...
x + y = 85
The total of charges is the sum of the products of charge per minute and minutes used:
7/20x + 2/5y = 31.00
We can eliminate the x-variable in these equations by multiplying the first by -7 and the second by 20, then adding the result.
-7(x +y) +20(7/20x +2/5y) = -7(85) +20(31)
-7x -7y +7x +8y = -595 +620 . . . . eliminate parentheses
y = 25 . . . . . . . . simplify
Then the value of x is
x = 85 -y = 85 -25
x = 60
