Determine the x-intercept of the quadratic function:
y=-0.25(x+1)^2+9

Y = ⁻¹/₄(x + 1)² + 9
0 = ⁻¹/₄(x + 1)² + 9
0 = ⁻¹/₄(x + 1)(x + 1) + 9
0 = ⁻¹/₄(x(x + 1) + 1(x + 1)) + 9
0 = ⁻¹/₄(x(x) + x(1) + 1(x) + 1(1)) + 9
0 = ⁻¹/₄(x² + x + x + 1) + 9
0 = ⁻¹/₄(x² + 2x + 1) + 9
0 = ⁻¹/₄(x²) - ¹/₄(2x) - ¹/₄(1) + 9
0 = ⁻¹/₄x² - ¹/₂x - ¹/₄ + 9
0 = ⁻¹/₄x² - ¹/₂x + 8³/₄
x = -(⁻¹/₂) ± √((⁻¹/₂)² - 4(⁻¹/₄)(8³/₄))
                       2(⁻¹/₄)
x = ¹/₂ ± √(¹/₄ + 8³/₄)
                 ⁻¹/₂
x = ¹/₂ ± √(9)
          ⁻¹/₂
x = ¹/₂ ± 3
        ⁻¹/₂
x = ¹/₂ + 3    U    x = ¹/₂ - 3
        ⁻¹/₂                     ⁻¹/₂
x = 4    U    x = -2¹/₂
    ⁻¹/₂                  ⁻¹/₂
x = -8    U    x = 5

21, i'm pretty sure it's right lol

The answers are 20,30,80,180,960,890,1230,4560. on the first row