Question

Помогите 5 задание Срочнооооооо

Answer 1

$\displaystyle\bf\\(5a-10)^{2}-(3a-8)^{2} +4a=\\\\=(5a)^{2}-2\cdot 5a\cdot 10+10^{2} -\Big[(3a)^{2} -2\cdot 3a\cdot 8+8^{2}\Big] +4a=\\\\=25a^{2} -100a+100-(9a^{2} -48a+64)+4a=\\\\=25a^{2} -100a+100-9a^{2} +48a-64+4a=\\\\=\underbrace{(25a^{2} -9a^{2} )}_{16a^{2}} +\underbrace{(48a+4a-100a)}_{-48a}+\underbrace{(100-64)}_{36}=\\\\=16a^{2} -48a+36=(4a)^{2}-2\cdot 4a\cdot 6+6^{2} =(4a-6)^{2} \\\\a=6\\\\(4a-6)^{2} =(4\cdot 6-6)^{2} =(24-6)^{2} =18^{2} =324\\\\Otvet \ : \ 324$