1.
а) 25ab^5 / 35a^4b = 5b^4 / 7a^3;
б) 4x / x^2 + 4x = 4x / x( x + 4) = 4 / x + 4;
в) 7a - 7b / a^2 - b^2 = 7( a - b) / (a - b)( a + b) = 7 / a + b;
г) 25x^2 - 16y^2 / 8y - 10x = (5x - 4y)(5x + 4y) / 2(4y - 5x) = - (5x - 4y)(5x + 4y) / 2(5x - 4y) = - 5x + 4y / 2.
2.
a) 2 - x^2 / x^2 - 2 - 4x / 4x = 8 - 4x^2 - (2x - 4x^2) / 4x^2 = 8 - 4x^2 - 2x + 4x^2 / 4x^2 = 8 - 2x / 4x^2 = 2( 4 - x) / 4x^2 = 4 - x / x^2;
б) 1 / х - 3 - 1 / x + 3 = 1 / x - 3 + 1 / x - 3 = 2 / x - 3;
в) 2 / а - 2 + 5 - 2a / a^2 - 2a = 2a + 5 - 2a / a^2 - 2a = 5 / a^2 - 2a.
3.
3c - 3b + 9c^2 / 3c = 9c^2 -(3b + 9c^2) / 3c = 9c^2 - 3b - 9c^2 / 3с = -3b / 3c;
Ecли c = 0,2, b = 3, то -3b / 3c = - 3 • 3 / 3 • 0,2 = -9 / 0,6 = - 15.
Ответ: - 15.
4.
2 / а + 2 / а + 2 - 4а / а^2 - 4 = 2а - 8 + 2а - 4 - 4а / а^2 - 4 = -4 - 4а / а^2 - 4 = -4( 1 + а) / а^2 - 4 = -4( 1 + а) / (а - 2)(а + 2).