Which classification best represents a triangle with side lengths 10 in., 12 in., and 15 in.? a) acute, because 10^2+12^2> 15^2 b) acute, because 12^2+15^2> 10^2 c) obtuse, because 10^2+12^2> 15^2 d) obtuse, because 12^2+15^2> 10^2

I'd apply the pythagorean theorem.(10 in)^2 + (12 in)^2 = (100 + 144)   in^2, or 244 in^2.   now compare that result to (15 in)^2, or 225.   since 244 > 225, the triangle is not a right triangle; its largest angle is greater than 90 deg, which makes this an obtuse triangle.you might want to draw a scale model of the triangle to see that this is the case.

Line ab is y = -7/5x + 56/5i don't understand  where point d comes into this.