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ICSE Class X Math 2013 Paper

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Question : 12 of 46
Marks: +1, -0
Solve the following equation and calculate the answer correct to two decimal places :
x2−5x−10=0x^2-5 x-10=0
Solution:  
Given : x2−5x−10=0x^2-5 x-10=0
Here, a=1,b=−5a=1, b=-5 and c=−10c=-10
∴    D  =b2−4ac\therefore \;\; D\;=b^2-4 a c
  =(−5)2−4×1×−10=65\; =(-5)^2-4 \times 1 \times -10=65
x  =  −b±D2ax\;=\;\frac{-b \pm \sqrt{D}}{2a}
  =  5±652×1\;=\;\frac{5 \pm \sqrt{65}}{2 \times 1}
  =  5±8.062\;=\;\frac{5 \pm 8.06}{2}
  =  5+8.062,  5−8.062\;=\;\frac{5+8.06}{2}, \;\frac{5-8.06}{2}
  =  13.062,−  3.062\;=\;\frac{13.06}{2}, -\;\frac{3.06}{2}
x  =6.53,−1.53x\;=6.53,-1.53
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