0\;npu\;Bcex\;x\\\\6.\;(2-x)(2+x)(4+x^2)+(6-x)^2=(4-x^2)(4+x^2)+36-12x+x^2=\\=16-x^4+36-12x+x^2=-x^4+x^2-12x+52" alt="4.\;(2x-7)(x+1)+3(4x-1)(4x+1)=2(5x-2)^2-53\\2x^2-5x-7+3(16x^2-1)=2(25x^2-20x+4)-53\\2x^2-5x-7+48x^2-3=50x^2-40x+8-53\\50x^2-5x-10=50x^2-40x-45\\35x=-35\\x=-1\\\\5.\;x^2-18x+84=(x^2-18x+81)+3=(x-9)^2+3>0\;npu\;Bcex\;x\\\\6.\;(2-x)(2+x)(4+x^2)+(6-x)^2=(4-x^2)(4+x^2)+36-12x+x^2=\\=16-x^4+36-12x+x^2=-x^4+x^2-12x+52" align="absmiddle" class="latex-formula">