Question

solve the equation by completing the square a^2+2a-35=0

Answer 1

a^2+2a-35=0
(a+7)(a-5)=0 (By factorization)

take (=0) for both sides,

a=-7 or a=5

Answer 2

Completing the square:

a^2 +2a -35=0 -- add (35);
a^2 +2a +K = 35 +K -- K = (b/2)^2 where b=2
a^2 +2a +1 = 35+1 -- factor the LHS into a perfect square;
add RHS together
(a+1)^2 = 36 -- take the square root of both sides
a+1 = 6 or a+1 = -6 --solve for "a"
a= 5 or a=(-7) -- check your answers to eliminate false hope :)

(5)^2 +2(5) -35 = 0
25 +10 -35 = 0
35 - 35 = 0 (a=5, is good)

(-7)^2 +2(-7) -35 = 0
49 - 14 - 35 = 0
49 - 49 = 0 (a=(-7), is good)

a= -7 and a=5

Answer 3

On a test, I would just factor like razmik did to get the answers; then double check :)