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Wittaler [7]
3 years ago
15

What is the factored form of x2 + 4xy − 21y2?

Mathematics
1 answer:
kow [346]3 years ago
8 0

Answer:

\mathrm{Factor}\:x^2+4xy-21y^2:\quad \left(x-3y\right)\left(x+7y\right)

Step-by-step explanation:

Given the expression

x^2+4xy-21y^2

We can write the expression by breaking it into the groups such as:

=\left(x^2-3xy\right)+\left(7xy-21y^2\right)

\mathrm{Factor\:out\:}x\mathrm{\:from\:}x^2-3xy\mathrm{:\quad }x\left(x-3y\right)

\mathrm{Factor\:out\:}7y\mathrm{\:from\:}7xy-21y^2\mathrm{:\quad }7y\left(x-3y\right)

=x\left(x-3y\right)+7y\left(x-3y\right)

\mathrm{Factor\:out\:common\:term\:}x-3y

=\left(x-3y\right)\left(x+7y\right)

Therefore,

\mathrm{Factor}\:x^2+4xy-21y^2:\quad \left(x-3y\right)\left(x+7y\right)

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It's a rotation clockwise of 90 degrees about the origin.

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4 years ago
40% of Oatypop cereal boxes contain a prize. Hannah plans to keep buying cereal until she gets a prize. What is the probability
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Answer:

(0.6)^{n}+n(0.4)(0.6)^{n-1}+\frac{n(n-1)(0.4)^{2}0.6^{n-2}}{2} +\frac{n(n-1)(n-2)0.4^{3}0.6^{n-3}}{6}

Step-by-step explanation:

We will use the binomial distribution. Let X be the random variable representing the no. of boxes Hannah buys before betting a prize.

Our success is winning the prize, p =40/100 = 0.4

Then failure q = 1-0.4  = 0.6

Hannah keeps buying cereal boxes until she gets a prize. Then n be no. times she buys the boxes.

P(X ≤ 3) = P(X=0) +P(X=1)+P(X=2)+P(X=3)

             = \binom{n}{0}p^{0}q^{n-0} +  \binom{n}{1}p^{1}q^{n-1}+ \binom{n}{2}p^{2}q^{n-2}+ \binom{n}{3}p^{3}q^{n-3}


             =  q^{n}+npq^{n-1}+\frac{n(n-1)(p)^{2}q^{n-2}}{2}+\frac{n(n-1)(n-2)p^{3}q^{n-3}}{6}

             = (0.6)^{n}+n(0.4)(0.6)^{n-1}+[tex]\frac{n(n-1)(0.4)^{2}0.6^{n-2}}{2} +\frac{n(n-1)(n-2)0.4^{3}0.6^{n-3}}{6}


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