Using the defects method, which relationship represents the law of cosines if the measure of the included angle between the sides a and b of δabc is less than 90°?
a) area of square c2 = -area of square a2 − area of square b2 + area of defect1 + area of defect2
b) area of square c2 = area of square a2 + area of square b2 + area of defect1 − area of defect2
c) area of square c2 = area of square a2 + area of square b2 − area of defect1 − area of defect2
d) area of square c2 = area of square a2 + area of square b2 + area of defect1 + area of defect2

Astudent found the solution below for the given inequality. |x-9|< -4 x-9> 4 and x-9< -4 x> 13 and x< 5 which of the following explains whether the student is correct? -the student is completely correct because the student correctly wrote and solved the compound inequality. -the student is partially correct because only one part of the compound inequality is written correctly. -the student is partially correct because the student should have written the statements using “or” instead of “and.” -the student is completely incorrect because there is no solution to this inequality.