Question

(a+5)²-(x-4)(x+4)+(x+3)(x-7)
даю 40 баллов помогите ​

Answer 1

$\displaystyle\bf\\(a+5)^{2} -(x-4)(x+4)+(x+3)(x-7)=\\\\=a^{2} +10a+25-(x^{2} -16)+x^{2} -7x+3x-21=\\\\=a^{2} +10a+25-x^{2} +16+x^{2} -4x-21=\\\\=a^{2} +10a+(\underbrace{x^{2} -x^{2}}_{0} )-4x+(\underbrace{25+16-21}_{20})=\\\\=a^{2} +10a-4x+20$