已知：b/a + c/a = 1 求证：b^2 + 4ac >= 0
问题描述：
已知：b/a + c/a = 1 求证：b^2 + 4ac >= 0
答
b+c=a
b^2 + 4ac
=b^2+4(b+c)c
=b^2+4c^2+4bc
=(b+2c)^2
某数的平方永远不小于0,故b^2 + 4ac >= 0
答
b/a + c/a = 1
b+c=a
b=a-c
b^2=a^2-2ac+c^2
b^2+4ac=a^2+2ac+c^2=(a+c)^2>=0
答
b/a + c/a = 1
b+c=a
b=a-c
b^2+4ac
=(a-c)^2+4ac
=a^2-2ac+c^2+4ac
=a^2+2ac+c^2
=(a+c)^2>=0