How do you solve #5r^2 = 80# using the quadratic formula?

2 Answers
Apr 24, 2018

Answer:

#+- 4#

Explanation:

#ax^2+bx+c=0#
#5r^2+0r+(-80)=0#

#x=(-b +- sqrt(b^2-4ac))/(2a)#
#r=(0+- sqrt(0^2-4*5*-80))/(2*5)#

#r=(0+- sqrt(0+1600))/10#
#r=+- 40/10#
#r=+- 4#

Apr 24, 2018

Answer:

#r=+-4#

Explanation:

#"Alternative method to quadratic formula"#

#"divide both sides by 5"#

#rArrr^2=16#

#color(blue)"take the square root of both sides"#

#rArrr=+-sqrt16larrcolor(blue)"note plus or minus"#

#rArrr=+-4#