SSC CHSL 16 Apr 2021 Shift 2 Paper

Section: Quantitative Aptitude

Question : 74 of 100

Marks: +1, -0

a^{2}+4 b^{2}+25 c^{2}+18

=2(a-2 b+20 c)

, then what is the value of

(a+2 b+5 c)

Solution:

Given,

a^{2}+4 b^{2}+25 c^{2}+18

=2(a-2 b+20 c)

a^{2}+1-2 a+4 b^{2}+1+4 b+25 c^{2}

+16-40 c=0

(a-1)^{2}+(2 b+1)^{2}+(5 c-4)^{2}=0

∴ \;\; a-1=0 ⇒ a=1

2 b+1=0 ⇒ b=-\;{1}/{2}

and

\;\; 5 c-4=0 ⇒ c=\;{4}/{5}

∴

The value of

(a+2 b+5 c)

=1+2 ×(-\;{1}/{2})+5 × \;{4}/{5}

=1-1+4=4

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