Solve.A plane flying with a tailwind flew at a speed of 420 mph, relative to the ground. When flying against the tailwind, it flew at a speed of 300 mph. Express these relationships as equations. Let x represent the speed of the plane in calm air and let y represent the speed of the wind.
A. x + y = 420
y = 300
B. x + y = 300
x - y = 420
C. x + y = 300
y = 420
D. x + y = 420
x - y = 300
Answer: D
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Find the magnitude or direction angle of the given vector as indicated.v = 7[(cos 135°)i + (sin 135°)j]; Find the direction angle ?.
A. 135° B. 225° C. 45° D. 30°
Find the reciprocal of the number.
A. 1
B. 0
C. 
D. 14
Round to the indicated place value.Round to the nearest tenth: -137.81
A. -137.7 B. -137.81 C. -137.8 D. -137
Find the center, foci, and vertices of the ellipse.
+ 
= 1
A. center at (0, 0)
foci at (0, -4) and (0, 4)
vertices at (0, -16), (0, 16)
B. center at (0, 0)
foci at (- 2
, 0) and (2
, 0)
vertices at (-4, 0), (4, 0)
C. center at (0, 0)
foci at (0, 4) and (2, 0)
vertices at (0, 16), (4, 0)
D. center at (0, 0)
foci at (0, - 2
) and (0, 2
)
vertices at (0, -4), (0, 4)