ICSE Class X Math 2013 Solved Paper

Question : 12 of 46

Marks: +1, -0

Solve the following equation and calculate the answer correct to two decimal places :

x^2-5 x-10=0

Solution:

Given :

x^2-5 x-10=0

Here,

a=1, b=-5

and

c=-10

∴ \;\; {\D}\;=b^2-4 a c

\;=(-5)^2-4 × 1 ×-10=65

x\;=\;{-b ± √{ {\D}}}/{2 a}

\;=\;{5 ± {√{65}}}/{2 × 1}

\;=\;{5 ± 8.06}/{2}

\;=\;{5+8.06}/{2}, \;{5-8.06}/{2}

\;=\;{13.06}/{2},-\;{3.06}/{2}

x\;=6.53,-1.53

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