Write a recursive and explicit formula for the following sequence: 21, 24, 27, ...
2 answers:
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<h3>Answer:</h3>
8x = 12
<h3>Explanation:</h3>Subtracting the first equation from the second, you get ...
... (5x +2y) -(3x +2y) = (7) -(5)
... 2x = 2 . . . . . the first answer choice is true
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Multiplying this expression for x by 4, we get
... 8x = 8 . . . . . the second answer choice (8x=12) is false
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Adding thee first equation to the second, you get ...
... (3x +2y) +(5x +2y) = (5) +(7)
... 8x +4y = 12
... 8 + 4y = 12 . . . . . . use the value of 8x just computed
... 4y = 4 . . . . . . . . . . subtract 8; the third answer choice is true
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<em>Alternate approaches</em>
In short, if you solve the system by any of the methods available, you find x=1 and y=1, so the second answer choice is clearly the correct one:
... 8x ≠ 12
By Cramer's method:
... x = (2·7-2·5)/(2·5-2·3) = 4/4 = 1
... y = (5·5-7·3)/4 = 4/4 = 1
By graphing, see attached.
By substitution (for 2y):
... 5x +(5-3x) =7 . . . . . using 2y=5-3x
... 2x = 2 . . . . . . subtract 5
... x = 1 . . . . . . . .divide by 2
... 5 -3·1 = 2y = 2 . . . . substitute x into the expression for 2y
... y = 1 . . . . . . . divide by 2
By matrix methods, see the second attachment. (x, y) = (1, 1), found in the rightmost column of the result.
The expression x^2 -7x + 10 can be written in factored form as given by Option C: (x-2)(x-5)
<h3>How to find the factors of a quadratic expression?</h3>If the given quadratic expression is of the form
then its factored form is obtained by two numbers alpha( α ) and beta( β) such that:
Then writing b in terms of alpha and beta would help us getting common factors out.
Sometimes, it is not possible to find factors easily, so using the quadratic equation formula can help out without any trial and error.
For this case, we're provided the expression:
We can write 10 as multiple of -5 and -2 and
we can write -7 as sum of -5 and -2. Thus, we get:
Thus, the expression x^2 -7x + 10 can be written in factored form as given by Option C: (x-2)(x-5)
Learn more about factorization of quadratic expression here: