Giải hệ phương trình sau bằng phương pháp gauss 2x1-3x2-2x3=2
3x1-2x2+3x3-x4=0
X1+x2+6x3-x4=-1
-3x1+7x2+6x3+x4=9

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is

Write a function for a rotation 90 degrees counter clockwise about the origin, point 0

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