One of the roots of the equation 4x ^ 2-x + c = 0 is 1.25 What is the second root.

1) Substitute the known root in the equation and calculate the value of the term with:

4 * (1.25) ^ 2 – 1.25 + c = 0;

4 * 1.5625 – 1.25 + c = 0;

6.25 – 1.25 + c = 0;

5 + c = 0;

c = -5.

2) We write the equation in the form and solve it using the discriminant:

4x ^ 2 – x – 5 = 0.

D = (-1) ^ 2 – 4 * 4 * (-5) = 1 + 80 = 81.

Let’s calculate the roots:

x1 = (- (- 1) + √81) / (2 * 4);

x1 = (1 + 9) / 8;

x1 = 10/8;

x1 = 1.25;

x2 = (- (- 1) – √81) / (2 * 4);

x2 = (1 – 9) / 8;

x2 = -8 / 8;

x2 = -1.

Thus, we find that the second root of the given equation is x = -1.

Answer: x = -1.