1) 33xy-9x^2+121y^2-33xy=9x^2+121y^2
(208²-11²):219 =(43264-121):219=43143:219=197
В) 49a^2 + 28ab + 4b^2- (12a^2 + 15ab -4ab - 5b^2)= 49a^2 + 28ab + 4b^2 -12a^2 - 15ab + 4ab + 5b^2 = 37a^2 + 17ab + 9b^2
a) на рисунке
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