Question #cd174

2 Answers
Dec 14, 2017

#x=-4+sqrt41#

#x=-4-sqrt41#

Explanation:

.

#x^2+8x-25=0#

To solve for #x#, you use the quadratic formula which is:

for a quadratic equation of general form:

#ax^2+bx+c=0#

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

Here, #a=1#, #b=8#, and #c=-25#

Therefore,

#x=(-8+-sqrt(8^2-4(1)(-25)))/(2(1))=(-8+-sqrt(64+100))/2#

#x=(-8+-sqrt164)/2=(-8+-sqrt(4(41)))/2=(-8+-2sqrt41)/2#

#x=(cancelcolor(red)2(-4+-sqrt41))/cancelcolor(red)2=-4+-sqrt41#

Answers to other problems:

#A).#, #y=3(x-1)^2#

From: #(a-b)^2=a^2-2ab+b^2#, our #a=x#, and #b=1), #we have:

#y=3(x^2-2x+1)#

#y=3x^2-6x+3#

#B).#, #y=2(x-3)(x+4)#

#y=2(x^2+4x-3x-12)=2(x^2+x-12)#

#y=2x^2+2x-24#

#A).#, #y=6(x-7)^2-2#

This equation is in the vertex form:

#y=a(x-h)^2+k# where the coordinates of the vertex are #(h,k)#

Out #h=7#, and #k=-2#, therefore, vertex is #(7,-2)#

#B).# #y=-1/2(x+10)²-12#

Vertex is #(-10,-12)#

Dec 14, 2017

#x = +-sqrt41 -4#

Explanation:

The trinomial does not factorise.

In #ax^2 +bx +c#, if #a =1 and b# is even, completing the square is a quick method.

#x^2 +8x-25=0" "larr# move the constant to the right

#x^2 +8x " "=25" "larr# add on # (b/2)^2# to both sides

#x^2 +8x +16 =25+16" "larr# the left side is a perfect square

#(x+4)^2 = 41#

#x +4 = +-sqrt41" "larr# consider positive and negative roots

#x = +-sqrt41 -4#