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3 years ago

Simplify:2(x2 + 5) − 3(x + 1) + 3

Mathematics

1 answer:

sesenic [268]3 years ago

3 0

Step-by-step explanation:

2x2 + 10 - 3x - 3 + 3

Solving like terms

2x2 - 3x + 10

Option B is the correct answer

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Rewrite 4/10 : 1/25 as a unit rate. A: 10:1 B: 25:4 C: 2:125 D: 100:1

Vladimir79 [104]

Answer:

4/10 : 1/25

4/10 / 1/25 = 4/10 x 25/1 = 100/10 = 10.

10 can also be written as 10:1, so A is correct.

Hope this helps!

6 0

3 years ago

How many congruent sides are on a Right Isosceles Triangle?

disa [49]

Answer:

I think it's 2.

3 0

3 years ago

4. A random variable X has a mean of 10 and a standard deviation of 3. If 2 is added to each value of X, what will the new mean

Ede4ka [16]

Adding 2 to each value of the random variable $X$ makes a new random variable $X+2$ . Its mean would be

$E[X+2]=E[X]+E[2]=E[X]+2$

since expectation is linear, and the expected value of a constant is that constant. $E[X]$ is the mean of $X$ , so the new mean would be

$E[X+2]=10+2=12$

The variance of a random variable $X$ is

$V[X]=E[X^2]-E[X]^2$

so the variance of $X+2$ would be

$V[X+2]=E[(X+2)^2]-E[X+2]^2$

We already know $E[X+2]=12$ , so simplifying above, we get

$V[X+2]=E[X^2+4X+4]-12^2$

$V[X+2]=E[X^2]+4E[X]+4-12^2$

$V[X+2]=(V[X]+E[X]^2)+4E[X]-140$

Standard deviation is the square root of variance, so $V[X]=3^2=9$ .

$\implies V[X+2]=(9+10^2)+4(10)-140=9$

so the standard deviation remains unchanged at 3.

NB: More generally, the variance of $aX+b$ for $a,b\in\mathbb R$ is

$V[aX+b]=a^2V[X]+b^2V[1]$

but the variance of a constant is 0. In this case, $a=1$ , so we're left with $V[X+2]=V[X]$ , as expected.

5 0

3 years ago

Suppose researchers marked 800 turtles and later were able to trap a total of 300 individuals in that population, of which 150 w

aleksklad [387]

The estimate for the total population size is 1600.

Setting up a proportion for this, we know that 150 out of our 300 turtle sample is marked; this is the first ratio for the proportion. We also know that we marked 800 of our total population, which we will call x:

150/300 = 800/x

Cross multiply:
150*x = 300*800
150x = 240000

Divide both sides by 150:
150x/150 = 240000/150
x = 1600

8 0

3 years ago

Calculate 20% of rs 250000

kenny6666 [7]

Answer:

50,000

Step-by-step explanation:

20% can be rewritten as 0.2 times 250000: 0.2*250000 = 50,000

5 0

2 years ago