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15. Consider the quadratic with equation y = ax + bx + c that passes through the points (1, 22), (6, 7) and (5, - 2). Equation 1: a+b+c 22 subtract Equation 3: 25a + 5b + c -2 to give Equation 4: 24 -24 a+ (-4) b and Equation 2: 36a + 6b + c = 7 subtract Equation 3: 25a + 5b + c = -2 to give Equation 5: 9 11 a+ 1 b 15c Next rearrange Equation 5 to make b the subject: V b=9 - 1la 15d Next substitute this result into Equation 4 to obtain an equation just in terms of a, and then solve for a. X a = Ca| 09 Enter your next step here4. Let U = V3 2 be a vector. U = 1 4b Determine the direction angle 0 of vector U, where 0'