A creature on the moon throws a rock off a cliff. the height of the rock above the surface of the moon, in meters, t seconds after it is thrown is given by h(t) = -t^2 +8t +10. when does the rock first reach a height of 12 meters?
+99 t^2-8t-10=0
t^2-8t=10
t^2-8t+16=10+16
(t-4)^2=26
t-4=+(26^(1/2))
t=4+(26^(1/2))
t=9.1s
+2668 −t2+8t+10=12
−t2+8t−2=0
t=−b±√b2−4ac2a
t=−8±√−82−(4×−1×−2)2×−1
t=−8±√56−2
t=−8±2√14−2
t=4±√14
t=4−√14
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