Answer:
x1 = -3
x2 = -5
y1 = -7
y2 = -15
Step-by-step explanation:
y = 4x +5
y = x2+12x+20
substitute y in second equation with first and solve quadratic equation
4x+5 = x² +12x + 20
x²+8x + 15 =0
D= b² - 4ac
a = 1
b = 8
c = 15
D = 64 - 60 = 4
D>0 => 2 real roots
x1 = [tex]\frac{-b+\sqrt{D} }{2a}[/tex]= (-8+2)/2 = -3
x2 =[tex]\frac{-b-\sqrt{D} }{2a}[/tex] = (-8-2)/2 = -5
having roots of x we can calculate y
y1 = 4x1+5 = 4*-3 +5 = -12 +5 = -7
y2 =4x2+5 = 4*-5+5 = -20 + 5 = -15
x1 = -3
x2 = -5
y1 = -7
y2 = -15
