Answer:
a = 1, b = - 12
Step-by-step explanation:
we know that x = 3 and x = - 4, so (x - 3) and (x + 4) must be the factors of the equation:
(x - 3)(x + 4)
x^2 + - 3x + 4x - 12
x^2 + x - 12
therefore a = 1 and b = - 12
Step-by-step explanation:
firstly substitute x=3 into [tex]x^{2} +ax+b=0[/tex]
[tex]3^{2} +3a+b=0[/tex]
9+3a+b = 0
b = -3a-9
secondly substitute x=-4 into [tex]x^{2} +ax+b=0[/tex]
[tex](-4)^{2} +(-4)a+b=0[/tex]
16-4a+b = 0
b = 4a-16
combine the equations above,
-3a-9 = b = 4a-16
so -3a-9 = 4a-16
7a = 7
a = 1
then substitute a = 1 into b = 4a-16 or b = -3a-9 (both are ok)
b = 4(1)-16 = -12 or b = -3(1)-9 = -12
