Answer:
1.63, -1.63
Step-by-step explanation:
y= -3x^2+16
if y is 8, then substitute that into the equation and solve for x
8=-3x^2+16
bring the variable and the constant to the other side
3x^2-8=0
factor 3 out (its ok if 8/3 isn't whole; do this to make the coefficient of x go)
x^2-8/3=0
This formula is recognizable. a^2-b^2 factors out to (a-b)(a+b)
a is x, b is [tex]\sqrt{8/3\\[/tex]
(x-[tex]\sqrt{8/3\\}[/tex])(x+[tex]\sqrt{8/3\\}[/tex])=0
so the appx x values for when y is 8 is the decimal form of [tex]\sqrt{8/3}[/tex] and -[tex]\sqrt{8/3}[/tex]
which is (keep in mind, i rounded this to the nearest 100th): 1.63 and -1.63
