Question

solve it.............................. with complete process
(HINT:If a^2+b^2+c^2=0, then a=b=c=0)

Answer 1

sum of three perfect squares,=0
that means every perfect square is zero itself..... as perfect squares can't be negative....

$(a - 1) {}^{2} = 0 \\ a = 1$

similarly
$b = - 2$
$c = - 1$
$2a - 3b + 7c \\ = 2 + 3 - 7 = - 2$