Question

Спростіть вираз (5-2х)( 5 + 2x) - (3 -2х)(4 -2х)

Answer 1

$\displaystyle\bf\\(5-2x)(5+2x)-(3-2x)(4-2x)=\\\\\\=5^{2} -(2x)^{2} -\Big(3\cdot 4-3\cdot 2x-2x\cdot 4-2x\cdot(-2x)\Big)=\\\\\\=25-4x^{2} -(12-6x-8x+4x^{2} )=\\\\\\=25-4x^{2} -(12-14x+4x^{2} )=\\\\\\=25-4x^{2} -12+14x-4x^{2} =\\\\\\=\underbrace{(-4x^{2} -4x^{2} )}_{-8x^{2} }+14x+\underbrace{(25-12)}_{13}=\\\\\\=-8x^{2} +14x+13$