How do I solve for X

Sarah is carrying out a series of experiments which involve using mcreasing amounts of a chemical. In the

Marianna [84]

Sarah is carrying out a series of experiments which involve using increasing amounts of a chemical. In the first experiment she uses 6g of the chemical and in the second experiment she uses 7.8 g of the chemical

(i)Given that the amounts of the chemical used form an arithmetic progression find the total amount of chemical used in the first 30 experiments

(ii)Instead it is given that the amounts of the chemical used for a geometric progression. Sarah has a total of 1800 g of the chemical available. Show that the greatest number of experiments possible satisfies the inequality: $1.3^N \leq 91$ and use logarithms to calculate the value of N.

Answer:

(a)963 grams

(b)N=17

Step-by-step explanation:

(a)

In the first experiment, Sarah uses 6g of the chemical

In the second experiment, Sarah uses 7.8g of the chemical

If this forms an arithmetic progression:

First term, a =6g

Common difference. d= 7.8 -6 =1.8 g

Therefore:

Total Amount of chemical used in the first 30 experiments

$S_n=\dfrac{n}{2}[2a+(n-1)d] \\S_{30}=\dfrac{30}{2}[2*6+(30-1)1.8] \\=15[12+29*1.8]\\=15[12+52.2]\\=15*64.2\\=963$ grams$

Sarah uses 963 grams in the first 30 experiments.

(b) If the increase is geometric

First Term, a=6g

Common ratio, r =7.8/6 =1.3

Sarah has a total of 1800 g

Therefore:

Sum of a geometric sequence

$S_n=\dfrac{a(r^N-1)}{r-1} \\1800=\dfrac{6(1.3^N-1)}{1.3-1} \\1800=\dfrac{6(1.3^N-1)}{0.3}\\$Cross multiply\\1800*0.3=6(1.3^N-1)\\6(1.3^N-1)=540\\1.3^N-1=540\div 6\\1.3^N-1=90\\1.3^N=90+1\\1.3^N=91$

Therefore, the greatest possible number of experiments satisfies the inequality

$1.3^N \leq 91$

Next, we solve for N

Changing $1.3^N \leq 91$ to logarithm form, we obtain:

$N \leq log_{1.3}91\\N \leq \dfrac{log 91}{log 1.3}\\ N \leq 17.19$

Therefore, the number of possible experiments, N=17

3 0

3 years ago

How do you solve x for (x+5)^3/2 = ( x-1)^3

malfutka [58]

Answer:

x = 6 (2^(1/3) + 2^(2/3)) + 7 or x = 6 (-2)^(1/3) ((-1)^(1/3) - 2^(1/3)) + 7 or x = 6 (-2)^(1/3) ((-2)^(1/3) - 1) + 7

Step-by-step explanation:

Solve for x:

1/2 (x + 5)^3 = (x - 1)^3

Expand out terms of the right hand side:

1/2 (x + 5)^3 = x^3 - 3 x^2 + 3 x - 1

Subtract x^3 - 3 x^2 + 3 x - 1 from both sides:

1 - 3 x + 3 x^2 - x^3 + 1/2 (x + 5)^3 = 0

Expand out terms of the left hand side:

-x^3/2 + (21 x^2)/2 + (69 x)/2 + 127/2 = 0

Bring -x^3/2 + (21 x^2)/2 + (69 x)/2 + 127/2 together using the common denominator 2:

1/2 (-x^3 + 21 x^2 + 69 x + 127) = 0

Multiply both sides by 2:

-x^3 + 21 x^2 + 69 x + 127 = 0

Multiply both sides by -1:

x^3 - 21 x^2 - 69 x - 127 = 0

Eliminate the quadratic term by substituting y = x - 7:

-127 - 69 (y + 7) - 21 (y + 7)^2 + (y + 7)^3 = 0

Expand out terms of the left hand side:

y^3 - 216 y - 1296 = 0

Change coordinates by substituting y = z + λ/z, where λ is a constant value that will be determined later:

-1296 - 216 (z + λ/z) + (z + λ/z)^3 = 0

Multiply both sides by z^3 and collect in terms of z:

z^6 + z^4 (3 λ - 216) - 1296 z^3 + z^2 (3 λ^2 - 216 λ) + λ^3 = 0

Substitute λ = 72 and then u = z^3, yielding a quadratic equation in the variable u:

u^2 - 1296 u + 373248 = 0

Find the positive solution to the quadratic equation:

u = 864

Substitute back for u = z^3:

z^3 = 864

Taking cube roots gives 6 2^(2/3) times the third roots of unity:

z = 6 2^(2/3) or z = -6 (-1)^(1/3) 2^(2/3) or z = 6 (-2)^(2/3)

Substitute each value of z into y = z + 72/z:

y = 6 2^(1/3) + 6 2^(2/3) or y = 6 (-1)^(2/3) 2^(1/3) - 6 (-1)^(1/3) 2^(2/3) or y = 6 (-2)^(2/3) - 6 (-2)^(1/3)

Bring each solution to a common denominator and simplify:

y = 6 (2^(1/3) + 2^(2/3)) or y = 6 (-2)^(1/3) ((-1)^(1/3) - 2^(1/3)) or y = 6 (-2)^(1/3) ((-2)^(1/3) - 1)

Substitute back for x = y + 7:

Answer: x = 6 (2^(1/3) + 2^(2/3)) + 7 or x = 6 (-2)^(1/3) ((-1)^(1/3) - 2^(1/3)) + 7 or x = 6 (-2)^(1/3) ((-2)^(1/3) - 1) + 7

7 0

3 years ago

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If someone bought 100 chocolate bars, and 5 sodas, and the 100 chocolate bars cost 100 dollars, and have to pay taxes, the total

MAXImum [283]

Not knowing the taxes the soda would be estimated to cost around 15$

3 0

3 years ago

Question is on picture

adoni [48]

Answer:

4 or 4/1 (both the same thing just with plotting point writing 4/1 is easier for me so I know to go up 4 over 1 :) )

Step-by-step explanation:

Parallel lines have the same slope, so both lines will have the same slope. Use line 1’s points to find the slope with the formula

(y1-y2)/(x1-x2)

(5-1)/(-2-(-3)

4/1=4

8 0

3 years ago

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Fast easy question!<br> The figures below are similar. What is the value of x

Ivahew [28]

Answer:

12

Step-by-step explanation:

6 0

3 years ago