Solve the literal equation ab+c=d in terms of a

Which statement is always true? a negative exponent cannot be part of an expression's numerator. a negative base raised to the power of 2 has a negative value. a negative base raised to the power of 2 has a positive value. any number to the first power is zero.

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

What are the measures of ∠a, ∠b, ∠c and ∠d? explain how to find each of the angles. measure need asap