1) (5a-3c)(5a+3c)-(7c-a)(7c+a) = 25a^2 - 9c^2 - (49c^2 - a^2) = 25a^2 - 9c^2 - 49c^2 + +a^2 = 26a^2 - 58c^2
2) (4b+10c)(10c-4b)+(-5c+2b)(5c+2b) = 100c^2 - 16b^2 + 4b^2 - 25c^2 = 75c^2 - 12b^2
2^7=128
2x=7
x=3.5
Ответ: Б
191
2x=-5
x=-2,5
192
3-2x=6
2x=-3
x=-1,5
194
1-2x=9
2x=-8
x=-4
195
2x+6=-6
2x=-12
x=-6
(a-3b)(c+d)= ac+ad -3bc -3bd