Question

упростите выражение 25x2-9/25x2-30x+9 при x=1.2

Answer 1

$\displaystyle\bf\\\frac{25x^{2} -9}{25x^{2} -30x+9} =\frac{(5x)^{2} -3^{2} }{(5x)^{2}-2\cdot 5x\cdot 3+3^{2} } =\frac{(5x-3)(5x+3)}{(5x-3)^{2} } =\\\\\\=\frac{5x+3}{5x-3} \\\\\\x=1,2\\\\\\\frac{5x+3}{5x-3} =\frac{5\cdot1,2+3}{5\cdot1,2-3}=\frac{6+3}{6-3} =\frac{9}{3} =3\\\\\\Otvet:3$