The two original functions are 4x+9y=7 and 4x-9y=9
To use the combination method, add all the values of the two equations together to cancel out one of the variables
4x+4x+9y-9y=7+9
8x=16
8x/8=16/8
x=2
4(2)+9y=7
8+9y=7
8-8+9y=7-8
9y=-1
y=-
Let x% be the salt concentration of first solution.
Then in 8ml, amount of salt = 
Given that to this 8ml solution, 11ml solution of a 47% salt solution is mixed.
amount of salt in 11ml of 47% salt solution is
= 
So, total amount of salt in new mixture = 
But given that this new solution is a 43% salt solution.
Hence amount of salt in new mixture of (8+11)=19ml solution of 43% salt solution is 
Hence 
8x+517 = 817
8x=817-517 = 300
x= 300/8 = 37.5
Hence the salt concentration in the first solution is 37.5%
Answer:
The number of mosquitoes is maximum for 6.5 inches rainfall.
Step-by-step explanation:
The given function is
.... (1)
where, M(x) is number of mosquitoes in millions and x the June rainfall in inches.
We need to find the rainfall that produces the maximum number of mosquitoes.
Differential the above function with respect to x.
.... (2)
Equate first derivative equal to 0.



Differential function (2) with respect to x.

Double derivative is negative. So, the value of function is maximum at x=6.5.
Therefore, the number of mosquitoes is maximum for 6.5 inches rainfall.
Answer:
ab = 1
Step-by-step explanation:
A Reciprocal of a number is a number which when multiplied by the original number yields the multiplicative number, 1.
So the reciprocal of x would be x⁻¹ or ¹⁄ₓ
The information we are given states that the sum of the two non-zero numbers a and b equals the sum of their reciprocals.
So we can write this into an equation and solve,
(See image)
Once we solve, we get the equation (ab-1)(a+b) = 0
We are given info that a+b≠0
So for the above equation to be true, ab-1 has to equal 0
For <em>this</em> to be true, the product ab must equal 1