Question

The area of a circle is given by the expression 9πx^2-12πx+4π. Find the radius of the circle, when x=4cm.​

Answer 1

★Given:-

• The area of a circle is given by the expression 9πx^2-12πx+4π.
• Value of  x=4cm

★To find:-

• The radius of circle.

★Solution:-

Given,

• Area = 9πx²-12πx+4π
• x = 4

Substituting value of x in the expression,

⇒ 9πx²-12πx+4π

⇒9π(4)²-12π(4)+4π

⇒ 144π - 48π + 4π

⇒ 100π.

We know:

✦Area of circle = πr²

Therefore,

⇒100π = πr²

⇒ r² = 100

⇒ r = 10cm

Hence,the radius of circle is 10cm.

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Know more:-

Important area formula's:

• Area of rectangle = l × b

• Area of square = (Side)²

• Area of Δ = 1/2bh

• Area of trapezoid =1/2(a + b)h

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