Can a obtuse triangle also be an equilateral triangle? explain

No. An obtuse triangle can not be an equilateral triangle because for a triangle to be equilateral, all three sides have to be the same measure and the same degree of angle (60). Since, an obtuse triangle has an angle greater than 90, the other two sides could be equal, but then you would have an obtuse isosceles triangle, not an equiangular equilateral triangle. Therefore, the obtuse angle in the obtuse triangle will limit the triangle from being an equilateral triangle.