Answer:
x =0 ±3/7 i sqrt(14)
Explanation:
7x^2 + 18 = 0
subtract 18 from each side
7x^2 = -18
divide by 7
x^2 = -18/7
take the square root of each side
sqrt(x^2) = ±sqrt(-18/7)
sqrt(x^2) = ±sqrt(-1) sqrt(18/7)
sqrt(-1) = i
x = ±isqrt(18/7)
x = ±isqrt(18)/sqrt(7)
x = ±isqrt(9)sqrt(2)/sqrt(7)
x = ±3i sqrt(2)/sqrt(7)
cannot leave a sqrt in the denominator
x = ±3i sqrt(2) * sqrt(7)/ (sqrt(7)* sqrt(7))
x = ±3i sqrt(14)/7
x = ±3/7 i sqrt(14)