Step One
Begin by getting one side of the question equal to zero.
32x -4 = 4x^2 + 60 Add - 32x + 4 from both sides.
0 = 4x^2 + 60 - 32x + 4 Collect like terms.
0 = 4x^2 - 32x + 64
Step Two
For this question, you could divide both sides by 4. It just makes the steps later on easier.
0 = x^2 - 8x + 16
Step Three
Calculate the discriminate.
The discriminate is b^2 - 4*a*c
a = 1; b = -8; c = 16
b^2 - 4*a*c = (-8)^2 - 4*(1)(16) = 64 - 64 = 0
There is only 1 root. It is real and it is rational.
A <<<<< Answer
Let's start by visualising this concept.
Number of grains on square:
1 2 4 8 16 ...
We can see that it starts to form a geometric sequence, with the common ratio being 2.
For the first question, we simply want the fifteenth term, so we just use the nth term geometric form:
Thus, there are 16, 384 grains on the fifteenth square.
The second question begs the same process, only this time, it's a summation. Using our sum to n terms of geometric sequence, we get:
Thus, there are 32, 767 total grains on the first 15 squares, and you should be able to work the rest from here.
Answer:
A. 4h 18min
Step-by-step explanation:
Apex
