x = ±sqrt(10)
step-by-step explanation:
5 - 2x² = -15
subtract 5 from each side
5-5 - 2x² = -15-5
-2x^2 = -20
divide by -2 on each side
-2x^2 /-2= -20/-2
x^2 =10
take the square root on each side
sqrt(x^2 )=±sqrt(10)
x = ±sqrt(10)
check:
5 - 2x² = -15
+sqrt(10)
5 - 2(sqrt(10))² = -15
5 -2(10) = -15
5 -20 = -15
-15 = -15
-sqrt(10)
5 - 2(-sqrt(10))² = -15
5 -2(10) = -15
5 -20 = -15
-15 = -15