a12x-6≥012x≥6x≥0,5x∈[0,5;∞)б2x²+7x-9≥0a+b+c=0⇒x1=1 U x2=c/a2+7-9=0⇒x1=1 U x2=-4,5 + _ +------------[-4,5]--------------[1]--------------------x∈(-∞;-4,5] U [1;∞)в9-2x≥02x≤9x≤4,5x∈(-∞;4,5]г21-4x-x²≥0x²+4x-21≤0D=16+84=100x1+x2=-4 U x1*x2=-21x1=-7 U x2=3 + _ +--------------[-7]------------------[3]--------------x⇒[-7;3]