Urgent math help needed will mark brainliest

Mathematics

1 answer:

iren [92.7K]3 years ago

3 0

Remark

Many calculators have a key that will do this in one step. Mine is one of them. So let's start with the answer and then we'll do it the long way.

9C3 = 84. You put it into your calculator as 9 2nF nCr 3 =

Solution

$\dfrac{9!}{(n - 3)!3!} = \dfrac{9*8*7*6!}{6!*3!}=\dfrac{9*8*7}{6}$

3*4*7 = 84 which is what you set out to show.

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2 years ago

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grigory [225]

Answer:

$4x^2+xy-18y^2=(4x+9y)\,(x-2y)$

Step-by-step explanation:

Let's examine the following general product of two binomials with variables x and y in different terms:

$(ax+by)\,(cx+dy)= ac\,x^2+adxy+bcxy+bdy^2$

so we want the following to happen:

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Notice as well that $ad+bc =1$ means that those two products must differ in just one unit so, one of them has to be negative, or three of them negative. Given that the product $bd=-18$ , then we can consider the case in which one of this (b or d) is the negative factor. So let's then assume that $a\,\,and \,\,c$ are positive.