Question

Solve. 3x^2 = –15x + 21
-5+_ i sqrt 3 / 2
5 +_ sqrt 53 / 2
5 +_ 3 sqrt 3 / 2
-5 +_ sqrt 23 / 2

Answer 1

use the quadratic formula
x = 1.14 and x = -6.1400

Answer 2

\[3x ^{2}+15x-21=0\]
cancelling 3
\[x ^{2}+5x-7=0\]
\[x=(-5\pm \sqrt{5^{2}-4*1*(-7)})/2\]
\[-5\pm \sqrt{53}/2\]