Помогите 1) (t² + 8t - 9) - (t² - 11t + 10) = 18t - 20 (уравнение) 2) -0.8c(c + 5) -...

1) ( $( t^{2} + 8*t - 9) - ( t^{2} -11 * t +10) = 18 * t - 20$
19 * t - 19 = 18 * t - 20
t = -1

2) $-0,8c^{2} (c+5) - 0,7(10c+5) + 0,8 c^{2} + 10c - 4 =$
$= -0,8 c^{2} -4c - 7c - 3,5 + 0,8 c^{2} +10c -4 =$
$= -c - 7,5$

3)3x(x-2)-(3x-1)(x+4) ≥ 8(2-x)
$3 x^{2} -6x-3 x^{2} +x-12x+4 \geq 16-8x$
-9x ≥ 12
x ≥ 12/(-9)

4) $( 2m^{5} n^{4} ) ^{7} * (4 m^{3} n^{5} ) ^{2} / (2 m^{4} n^4) ^{10} }$ =
= $(2 m^{5} n^{4}) ^{7} * (4m^{3} n^{5} ) ^{2} / ((2 m^{4} n^{4}) ^{7} * (2 m^{4} n^{4}) ^{3})$ =
= $( m^{7} * (4 m^{3} n^{5} ) ^{2} )/(2 m^{4} n^{4} ) ^{3}$ =
= $m^{7} * 2^{4} * ( m^{3} n^{5} ) ^{2} / 2^{3} * ( m^{4} n^{4} ) ^{2} * m^{4} n^{4}$ =
= $2 m^{7} m^{-2} n^{-2} / m^{4} n^{4}$ = $2*m/ n^{2}$