1)7x²+8x+1 = 0
Так как a-b+c = 0(7-8+1 = 0):
x1 = -1
x2 = -c/a = -1/7
2)(y-3)(y+3) = 5y-13
y²-9-5y+13 = 0
y²-5y+4 = 0
Так как a+b+c = 0(1-5+4 = 0):
y1 = 1
y2 = c/a = 4
3)x²+2x/2 = x²+24/7
7(x²+2x)/14 = 2(x²+24)/14
7x²+14x = 2x²+48
5x²+14x-48 = 0
D/4 = (b/2)²-ac = 49+240 = 289 = 17 = 17²
x1 = (-(b/2)+√D/4)/a = -7+17/5 = 10/5 = 2
x2 = -7-17/5 = -24/5 = -4.8