Question

What is the solution to the equation? 2 x squared plus 4 equals 20 Choose all answers that are correct.

a. − 2 square root of 2
b. − 2 square root of 8
c. 2 square root of 2
d. 2 square root of 8

Answer 1

`2x^2+4=20\ \ \ \ |subtract\ 4\ from\ both\ sides\\\\2x^2=16\ \ \ \ \ |divide\ both\ sides\ by\ 2\\\\x^2=8\iff x=\pm\sqrt8\\----------------------------\\\sqrt8=√(4\cdot2)=\sqrt4\cdot\sqrt2=2\cdot\sqrt2=2\sqrt2\ \ \ |use\ √(a\cdot b)=√(a)\cdot√(b)\\-----------------------------\\therefore\ your\ answer\ is\ -2\sqrt2\ and\ 2\sqrt2\to\boxed{a\ and\ c}`