ПОМОГИТЕ ПОЖАЛУЙСТА ДАЮ 50Б.номер 1 Упростить (4а-в)^2+(2а-в)(2а+в) номер 2 График...

Решите задачу:

$1)\; \; (4a-b)^2+(2a-b)(2a+b)=\\\\=16a^2-8ab+b^2+4a^2-b^2=20a^2-8ab=4a(5a-2b)\\\\2)\; \; \left \{ {{7=-k+b} \atop {1=b}} \right. \; \left \{ {{k=b-7} \atop {b=1}} \right. \; \left \{ {{k=-6} \atop {b=1}} \right. \; \; \; \yo \; \; y=-6x+1\\\\3a)\; \; \left \{ {{4x+3y=-12} \atop {5x-3y=30}} \right. \; \left \{ {3{y=-12-4x} \atop {5x-(-12-4x)=30}} \right. \left \{ {{3y=-12-4x} \atop {9x=18}} \right. \\\\ \left \{ {{3y=-12-8} \atop {x=2}} \right. \; \left \{ {{3y=-20} \atop {x=2}} \right. \; \left \{ {{y=-20/3} \atop {x=2}} \right. \; \left \{ {{y=-6\frac{2}{3}} \atop {x=2}} \right.\; \; \to \; (2,\, -6\frac{2}{3})$

$3b)\; \; \left \{ {{4x+y=1\; |\cdot 2} \atop {x-2y=7}} \right. \oplus \left \{ {{9x=9} \atop {2y=x-7}} \right. \; \left \{ {{x=1} \atop {2y=-6}} \right.\; \left \{ {{x=1} \atop {y=-3}} \right. \; \; \to \; \; (1,-3)$