How do you factor a perfect square trinomial 9x^2 − 12x + 49x212x+4?

1 Answer
Jul 7, 2015

9x^2-12x+4=(3x-2)^29x212x+4=(3x2)2

Explanation:

If Ax^2+Bx+C = (ax+c)^2Ax2+Bx+C=(ax+c)2 is a perfect square trinomial
then for some set {a,c}{a,c}
color(white)("XXXX")XXXXA=a^2A=a2
color(white)("XXXX")XXXXC=c^2C=c2
and
color(white)("XXXX")XXXXB = 2acB=2ac

Given that 9x^2-12x+49x212x+4 is a perfect square trinomial
color(white)("XXXX")XXXXA=9x^2 rarr a=3xA=9x2a=3x
color(white)("XXXX")XXXXC=4 rarr c=+-2C=4c=±2

Since B=-12x = 2ac = 2(3x)cB=12x=2ac=2(3x)c
color(white)("XXXX")XXXXrarr c=-2c=2