Math homework Help?

Question

Section 11.7: Let's take on problems #67 [What is wrong with the following? Explain the correct method of solution.
(x - 3)(x + 4) = 8
x - 3 = 8 or x + 4 = 8
x = 11 or x = 4]
and #68 [What is incorrect about solving x^2 = 3x by dividing both sides by x?], in order. Both problems involve detailed explanations for each step!

Answer 1

(x-3)(x+4)=8
x^2+x-12=8
x^2+x-20=0
(x-4)(x-5)=0
x=4
x=5


for x^2=3x
divide by x
x=3
there is nothing incorrect about dividing by x

Answer 2

the incorrect thing about dividing by x is that u will neglect 0 as answer which can deduct u r marks as it has deducted mine once.

well when u are doing (x-3)(x-4)=8
the method u are applying works only when u have 0 on right hand side because then the condition is that if we divide either of terms by zero the left will give 1 value of x .but how can u apply this over here. right method (x-3)(x+4)=8
x^2+x-12=8
x^2+x-20=0
(x-5)(x-4)=0
x=4,x=5

one hing more if u get 2 same values do write them as many times they appear because 1 time i loose my marks because of that

Answer 3

X = 4.

4-3 = 1
x+4 = 8
1*8 = 8

Answer 4

(x-3)(x+4)=8
sqx+4x-3x-12=8
sqx+x=20
that's all i could get
btw you NEVER divide by an unknown

Answer 5

I am no good at Algebra, but you might find the help you need at mathleague.com Good Luck