If it's x²y³ then we know it's the second term of the expansion, that known we can use the combination
C(5, 2) = 5!/(2!.3!) = 10
Then if we had something like
(a + b)^5 our second term would be 10a²b³ but as we can see it's "a²"
And in our case we have 2x as a
So we must do 2² too
2² = 4
10 . 4 = 40
Then our second term of the expansion would be
40x²y³
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Sn=A1(1-r^n)/(1-r)
Sum of a finite geometric series formula
We know the sum, number of terms and rate, so you plug those in.
-255=A1(1-(-4)^4))/(1-(-4)
-255=A1(1-256)/5
-255=A1(-255)/5
-1275=A1(-255)
5=A1
Hope this helped! Let me know if you have any questions.
<span>The number of cell phone minutes used by high school seniors follows a normal distribution with a mean of 500 and a standard deviation of 50. what is the probability that a student uses more than 580 minutes?
Given
μ=500
σ=50
X=580
P(x<X)=Z((580-500)/50)=Z(1.6)=0.9452
=>
P(x>X)=1-P(x<X)=1-0.9452=0.0548=5.48%
</span>
