How did they get -3 for this problem?

Step-by-step explanation:

Solve x^2 + 6x + 4.  Here the coefficients of the quadratic are a = 1, b = 6 and c = 4.  The discriminant is therefore b^2-4ac, or, in this case, 6^2-4(1)(4), or 20.

The roots are:

      -6 ± √20  

x = = -3 ± √4√5:  x = -3 + 2√5 and x = -3 - 2√5

             2

The -3 comes from the -6/2 in the application of the quadratic formula.

Answer A is correct.

∠acb = 8°

step-by-step explanation:

∠xba lies on the circle and is half the measure of the intercepted arc ax

hence

measure of arc ax = 2 × 42° = 84°

∠acb is outside the circle and is

∠acb = (arcab - arcax ), hence

∠acb = 0.5 (100 - 84) = 0.5 × 16° = 8°

21/58.

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