Question

мне только 4 пожалуйста
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Answer 1

$\displaystyle\bf\\\left \{ {{10x+12y=7,5} \atop {24y-5x=-5}} \right. \\\\\\\left \{ {{10x+12y=7,5} \atop {-5x+24y=-5} \ |\cdot2} \right.\\\\\\+\left \{ {{10x+12y=7,5} \atop {-10x+48y=-10}} \right. \\------------\\60y=-2,5\\\\y=-\frac{1}{24} \\\\\\10x=7,5-12y=7,5-12\cdot\Big(-\frac{1}{24} \Big)=7,5+\frac{1}{2} =7,5+0,5=8\\\\\\x=8:10=0,8\\\\\\x_{0} =0,8 \ \ ; \ \ y_{0} =-\frac{1}{24}\\\\\\7x_{0} +3y_{0} =7\cdot 0,8+3\cdot\Big(-\frac{1}{24} \Big)=5,6-\frac{1}{8} =5,6-0,125=5,475$