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2 years ago

The product of 5 and a number, decreased by 9, is 306. What is the number?

Mathematics

2 answers:

densk [106]2 years ago

7 0

Answer:

The number is 63

Step-by-step explanation:

Product means multiply

Decreased by 9

5n-9

Is means equals

5n-9 = 306

Solve

5n-9 = 306

Add 9 to each side

5n-9+9 = 3-6+9

5n = 315

Divide by 5

5n/5 = 315/5

n = 63

steposvetlana [31]2 years ago

5 0

Step-by-step explanation:

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Find the Center and the radius of the circle<br> x2 + y2 - 6x + 8y- 7 = 0.

777dan777 [17]

Answer:

C(3,-4), r=4*sqrt(2)

Step-by-step explanation:

C(p, q)

x^2+y^2+dx+ey+f=0

p=-d/2, q=-e/2, r^2=p^2+q^2-f

x^2+y^2 - 6x+8y-7=0

p=-(-6)/2=6/2=3

q=-8/2=-4

r^2=3^2 +(-4)^2+7

r^2=9+16+7

r^2=32

r=sqrt(32)

r=sqrt(16*2)

r=4*sqrt(2)

8 0

3 years ago

Solve y'' + 10y' + 25y = 0, y(0) = -2, y'(0) = 11 y(t) = Preview

svetlana [45]

Answer: The required solution is

$y=(-2+t)e^{-5t}.$

Step-by-step explanation: We are given to solve the following differential equation :

$y^{\prime\prime}+10y^\prime+25y=0,~~~~~~~y(0)=-2,~~y^\prime(0)=11~~~~~~~~~~~~~~~~~~~~~~~~(i)$

Let us consider that

$y=e^{mt}$ be an auxiliary solution of equation (i).

Then, we have

$y^prime=me^{mt},~~~~~y^{\prime\prime}=m^2e^{mt}.$

Substituting these values in equation (i), we get

$m^2e^{mt}+10me^{mt}+25e^{mt}=0\\\\\Rightarrow (m^2+10y+25)e^{mt}=0\\\\\Rightarrow m^2+10m+25=0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~[\textup{since }e^{mt}\neq0]\\\\\Rightarrow m^2+2\times m\times5+5^2=0\\\\\Rightarrow (m+5)^2=0\\\\\Rightarrow m=-5,-5.$

So, the general solution of the given equation is

$y(t)=(A+Bt)e^{-5t}.$

Differentiating with respect to t, we get

$y^\prime(t)=-5e^{-5t}(A+Bt)+Be^{-5t}.$

According to the given conditions, we have

$y(0)=-2\\\\\Rightarrow A=-2$

and

$y^\prime(0)=11\\\\\Rightarrow -5(A+B\times0)+B=11\\\\\Rightarrow -5A+B=11\\\\\Rightarrow (-5)\times(-2)+B=11\\\\\Rightarrow 10+B=11\\\\\Rightarrow B=11-10\\\\\Rightarrow B=1.$