Use Pascal’s triangle and binomial expansion strategies (x+y)^3
1 answer:
<h2>1. Pascal’s triangle</h2>
Pascal's triangle is an strategy in math that stands for a triangular array we use to solve problems of binomial coefficients. This strategy is called after the mathematician Blase Pascal. It consists in number patters. So in this problem we need to solve this following Pascal’s triangle strategy:
The strategy consists in building a triangle. So 1 is the first and last numbers in each row of Pascal’s Triangle. Next, every other number in each row is formed when you add the two numbers directly above the number, as shown in Figure below. So:
A binomial is a polynomial having two terms. So binomial expansion is a method that stands for a formula that gives us a quick method of raising a binomial to a power. So, for n=3, the binomial expansion can be written as:
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So there are 3 siblings: the first twin, the second twin, and their older sister.
Since the sister is older by 11 years, you can represent their relationship with the following equation;
age of twin = age of older sister - 11
t = s - 11
Representing this next part may be a little hard to show, but i'll do my best :)
Adding the ages together can be represented like this;
total age = t + t + s
If the product of their ages ( t * t * s ) is 1181 more than the sum, you can show it like this:
Now you substitute in (s - 11) for t because s = t - 11.
Factor:
Since it's a third-degree equation, I just entered it into a polynomial solver in my calculator. There was only one factor listed, x = 19. Using (s - 19) = 0 as a factor, the equation becomes the following:
Using the quadratic formula, you get:
Since you have a square root of a negative number, the answer will be imaginary. You cannot have an age that is imaginary, so the age of the older sister (s) is 19 years.
Because t = s - 11, that means that t = (19) - 11 = 8.
t is the age of the twins, so the twins are 8 years old.
Since the sister is older by 11 years, you can represent their relationship with the following equation;
age of twin = age of older sister - 11
t = s - 11
Representing this next part may be a little hard to show, but i'll do my best :)
Adding the ages together can be represented like this;
total age = t + t + s
If the product of their ages ( t * t * s ) is 1181 more than the sum, you can show it like this:
Now you substitute in (s - 11) for t because s = t - 11.
Factor:
Since it's a third-degree equation, I just entered it into a polynomial solver in my calculator. There was only one factor listed, x = 19. Using (s - 19) = 0 as a factor, the equation becomes the following:
Using the quadratic formula, you get:
Since you have a square root of a negative number, the answer will be imaginary. You cannot have an age that is imaginary, so the age of the older sister (s) is 19 years.
Because t = s - 11, that means that t = (19) - 11 = 8.
t is the age of the twins, so the twins are 8 years old.
7π/12 lies in the second quadrant, so we expect cos(7π/12) to be negative.
Recall that
which tells us
Now,
and so