How do you find the roots, real and imaginary, of y=4x^2 +x -3-(x-2)^2 y=4x2+x3(x2)2 using the quadratic formula?

1 Answer
Jan 23, 2016

x=0.9067 and x=-2.5734x=0.9067andx=2.5734

Explanation:

first, expand the bracket

(x-2)^2(x2)2

(x-2)(x-2)(x2)(x2)

x^2-4x+4x24x+4

then, solve the equations

y=4x^2+ x-3-(x^2-4x+4)y=4x2+x3(x24x+4)

y=4x^2+ x-3-x^2+4x-4y=4x2+x3x2+4x4

y=3x^2+ 5x-7y=3x2+5x7

then, by using b^2-4acb24ac

for the equation: y=3x^2+ 5x-7y=3x2+5x7

where a=3, b=5 and c=-7a=3,b=5andc=7 into b^2-4acb24ac

5^2-4(3)(-7)524(3)(7)

25--842584

109109

so, compare to this

b^2-4ac>0b24ac>0 : two real and different roots
b^2-4ac=0b24ac=0 : two real root and equals
b^2-4ac<0b24ac<0 : no real roots or (the roots are complexes)

so, 109>0109>0 means two real and different roots

thus, you must use this formula to find the imaginary roots

x= (-b+- sqrt(b^2-4ac ))/ (2a)x=b±b24ac2a

x= (-5+- sqrt(5^2-4(3)(-7) ))/ (2(3)x=5±524(3)(7)2(3)

x= (-5+- sqrt(109))/ 6x=5±1096

x= (-5+sqrt(109))/ 6x=5+1096 and x= (-5- sqrt(109))/ 6x=51096

solve it and u will get the values of x which is

x=0.9067 and x=-2.5734x=0.9067andx=2.5734