Solve this linear system using matrices:

x1 + 2x2 − x3 = −4
x1 + 2x2 + x3 = 2
−x1 − x2 + 2x3 = 6
x1=
x2=
x3

Look at the figure below: triangle abc is a right triangle with angle abc equal to 90 degrees. the length of ac is 5 units and the length of ab is 4 units. d is a point above c. triangle adc is a right triangle with angle dac equal to 90 degrees and dc parallel to ab. what is the length, in units, of segment cd?