Monday 6 October 2014

CIRCLES 3


Find y in the figure below;


Solution

From circle geometry,
(QR)(QS) = (PQ)2
y(y + 21) = 102
y2 + 21y = 100
y2 + 21y – 100 = 0

We factorize by splitting the middle term: 21y = (25y – 4y).

y2 + 25y – 4y – 100 = 0
(y2 + 25y) – (4y – 100) = 0
y(y + 25) – 4(y + 25) = 0
(y - 4)( y + 25) = 0                              
y - 4 = 0  OR  y + 25 = 0
y = 4 OR y = -25 

Since we don’t have negative length, we take y = 4cm

TRY THIS……..


Find y in the figure below;




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