Question

Help me Please!! Ive got a deadline!! Thanks! (:

Answer 1

The equation in standard form is 2x^2 + 7x - 15=0. Factoring it gives you (2x-3)(x+5)= 0. That's the first one.  The second one requires you to now your formula for the axis of symmetry which is x = -b/2a with a and b coming from your quadratic.  Your a is -1 and your b is -2, so your axis of symmetry is
x= -(-2)/2(-1) which is x = 2/-2 which is x = -1.  That -1 is the x coordinate of the vertex.  You could plug that back into the equation and solve it for y, which is the easier way, or you could complete the square on the quadratic...let's plug in x to find y.  -(-1)^2 - 2(-1)-1 = 0.  So the vertex is (-1, 0).  That's the first choice given.  For the last one, since it is a negative quadratic it will be a mountain instead of a cup, meaning it doesn't open upwards, it opens downwards.  Those quadratics will ALWAYS have a max value as opposed to a min value which occurs with an upwards opening parabola.  This one is also the first choice because of the way the equation is written.  There is no side to side movement (the lack of parenthesis tells us that) so the x coordinate for the vertex is 0.  The -1 tells us that it has moved down from the origin 1 unit; hence the y coordinate is -1.  The vertex is a max at (0, -1)