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3.
The sides of a rectangle are x cm and (x + 1) cm. A circle has radius of (x + 2) cm. If the
22
sum of the area of the rectangle and the circle is 184 cm². Using n as 22/7find the value of x.


Sagot :

Answer:

x = 5.00 cm

Step-by-step explanation:

• area of the rectangle = [tex]x[/tex]   x   [tex](x + 1)[/tex]

                                     = [tex]x^2 + x[/tex]

• area of the circle = π r²

                               = [tex]\frac{22}{7}[/tex]   x   [tex](x + 2)^2[/tex]

                               = [tex]\frac{22}{7}[/tex]   x   [tex](x^2 + 4x + 4)[/tex]

∴   [tex]x^2 + x[/tex]   +    [tex]\frac{22}{7}[/tex]   x   [tex](x^2 + 4x + 4) = 184[/tex]  

⇒  [tex]x^2 + x[/tex]      +   [tex]\frac{22}{7} x^2 \space\ + \space\ \frac{88}{7} x \space\ + \space\ \frac{88}{7} = 184[/tex]

⇒  [tex]\frac{29}{7}x^2 \space\ + \space\ \frac{95}{7}x \space\ - \frac{1200}{7} = 0[/tex]

• Using quadratic formula, where

a = [tex]\frac{29}{7}[/tex]

b = [tex]\frac{95}{7}[/tex]

c = [tex]\frac{-1200}{7}[/tex] ,

[tex]x=\frac{-b \pm \sqrt{b^2-4c}}{2}[/tex]

[tex]x = \frac{-\frac{95}{7}\pm \sqrt{(\frac{95}{7})^2 - 4(\frac{29}{7})(\frac{-1200}{7} ) } }{2(\frac{29}{7})}[/tex]

[tex]x = 5.00 \space\ \space\ \space\ or \space\ \space\ \space\ x = -8.28[/tex]

As length (x) cannot be a negative number,

x = 5.00 cm