Q) how to solve by completing the square method ? a) #2x^2+16x+5# b) #6+4x-x^2#

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Answer 1 · 2017-12-25T11:02:46

a)Solution: #x~~ -0.33 , x~~-7.67#
b)Solution: #x~~ -1.16 , x~~ 5.16#

a) #2x^2+16x+5=0 or 2(x^2+8x) +5=0# or

#2(x^2+8x+16)-32 +5=0# or

#2(x+4)^2=27 or (x+4)^2=27/2 or (x+4)^2=13.5# or

#(x+4)=+-sqrt13.5 or x ~~-4+-3.674# or

# x ~~-4+-3.674 :. x~~ -0.33(2dp) , x~~-7.67(2dp)#

Solution: #x~~ -0.33 , x~~-7.67# [Ans]

b) #-x^2+4x+6=0 or -(x^2-4x) +6=0# or

#-(x^2-4x+4) +4+6=0 or (x^2-4x+4)=10# or

#(x-2)^2=10 or x-2 = +-sqrt10# or

#x = 2+-sqrt10:. x ~~ 5.16(2dp) , x~~ -1.16(2dp)#

Solution: #x~~ -1.16 , x~~ 5.16# [Ans]