The formula to find area of a circle is A=π $r^{2}$ . A is area, and r is for radius. Since we have the diameter here, we just need to divide by 2 to find the radius. 8÷2=4, so there, the radius is 4. Now we need to square 4, and do 4x4, which equals 16. Now to multiply 16 by π, or 3.14. 16 x 3.14 = 50.24. The final answer is 50.24 $cm^{2}$ . Hope this helped! :]

8 0

3 years ago

Question number 8. Prove that 3 + √5 is an irrational number.

Marina86 [1]

Answer :

Let's assume the opposite of the statement i.e., 3 + √5 is a rational number.

$\\ \sf \: 3 + \sqrt{5} = \frac{a}{b} \\ \\ \qquad \: \tiny \sf{(where \: \: a \: \: and \: \: b \: \: are \: \: integers \: \: and \: \: b \: \neq \: 0)} \\$

$\\ \sf \: \sqrt{5} = \frac{a}{b} - 3 = \frac{a - 3b}{b} \\$

Since, a, b and 3 are integers. So,

$\\ \sf \: \frac{p - 3b}{b} \\ \\ \qquad \tiny \sf{ \: (is \: \: a \: \: rational \: \: number \:) } \\$

Here, it contradicts that √5 is an irrational number.

because of the wrong assumption that 3 + √5 is a rational number.

$\\$

Hence, 3 + √5 is an irrational number.

7 0

3 years ago

How many solutions does this equation have x^4 - 6x^2 -7 = 0

NNADVOKAT [17]

Answer:

2 solutions

Step-by-step explanation:

x^4-6x^2-7=0

Replace x^2 by y

(x^2)^2-6x^2-7=0

y^2-6y-7=0

D=b^2-4ac= (-6)^2-4*1*(-7)= 36+28=64

sqrtD=8

y1=(-b-sqrtD)/2a=-2/2=-1

y2= (-b+sqrtD)/2a=14/2=7

x^2=-1(n0 roots) x^2=7 x=sqrt7 or x=-sqrt7

2 roots

5 0

3 years ago