Six million and seventy two hundred. 6.0072 x 10*
*=6
Answer:
a= 2b-x
Step-by-step explanation:
You have to isolate the variable by dividing each side of the factors that does not contain the variable "a".
I'll use subscript notation for brevity, i.e.
.
By the chain rule,



We have

and

When
, we have

and the partial derivatives take on values of

So we end up with

I'm assuming the funds earn 5% yearly?
Call x the amount he saves every year. The first year's deposit will be multiplied by 1.05 three times, the next will be multiplied by 1.05 twice, the third will be multiplied by 1.05 once, and the fourth will not generate interest (as it will immediately be used to buy the car).
Therefore, x(1.05^3+1.05^2+1.05+1)=21000, so 4.31x=21000. Dividing by 4.31, we see that x is approximately equal to 4872.