Mischa wrote the quadratic equation 0 = –x2 + 4x – 7 in standard form. what is the value of c in her equation?

How do i do this? i don’t understand

With these 5 geometry questions! pls 1.)quadrilateral abcd is inscribed in this circle.what is the measure of ∠a ? enter your answer in the box.°2.)quadrilateral abcd is inscribed in a circle.what is the measure of angle a? enter your answer in the box.m∠a= 3.)quadrilateral abcd is inscribed in this circle.what is the measure of angle b? enter your answer in the box.m∠b= °4.)quadrilateral abcd is inscribed in this circle.what is the measure of angle a? enter your answer in the box.°5.) quadrilateral abcd is inscribed in this circle.what is the measure of angle c? enter your answer in the box.°

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.