Question

solve the following.

(X-8) (X+7) = 5

Answer 1

@UnkleRhaukus , help please?

Answer 2

expand the left hand side of the equation using foil


\[(\overbrace{\overbrace{\color{orange}a
+\underbrace{\color{cornflowerblue}b)(\color{seagreen}c}_{\text{Inside}}}^{\text{First}}
+\color{brown}d}^{\text{Outside}})
=\overbrace{\color{orange}a\color{seagreen}c}^\text F
+\overbrace{\color{orange}a\color{brown}d}^\text O
+\underbrace{\color{cornflowerblue}b\color{seagreen}c}_\text I
+\underbrace{\color{cornflowerblue}b\color{brown}d}_\text L\\
\qquad\quad \underbrace{\qquad\qquad}_{\text{Last}}\]

Answer 3

How'd you do the colors?

Answer 4

majix

Answer 5

(x^2+7x-8x-56)=5
(x^2-x-56)=5
I subtract 56 from the 5, right? Or vice versa?

Answer 6

x^2-x-56 = 5 is good work

now take-away 5 from both sides

Answer 7

x^2-x-61

Answer 8

yeah, x^2-x-61 = 0


now you could use completing the square method, or the quadratic formula

Answer 9

(the solutions very aren't nice, they have fractions and square-roots in them)

Answer 10

Ooooooh nooooooo ! :/

Answer 11

Just use the quadratic formula. It will save you from your fear.

Answer 12

A Quadratic Equation\[ax^2+bx+c=0\]
The Quadratic Formula\[x_{1,2}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}\]
Factored for of the Quadratic Equation\[(x-x_1)(x-x_2)=0\]
___________

Start by identifying the coefficients a,b,c

Compare
\[x^2-x-61=0\]
With
\[ax^2+bx+c=0\]
\[a=?\\
b=?\\
c=?\]

Answer 13

@cookiibabii93, can you find a,b,c ?

Answer 14

a=x, b=x, c=-61

Answer 15

c = -61 is right

but not a nor b

Answer 16

a & b is 1

Answer 17

a =1
b =
c= -61

Answer 18

-1

Answer 19

thats better

Answer 20

plug these into the quadratic formula to get

\[x_{1,2}=\frac{-(-1)\pm\sqrt{(-1)^2-4(1)(-61)}}{2(1)}\]

Answer 21

\[\frac{ 1\pm \sqrt{1-244} }{ 2 }\]

Answer 22

careful the minus should be a plus

Answer 23

Ooooh, there's where I messed up at, my answer was negative...I knew that was wrong

Answer 24

\[\frac{ 1\pm \sqrt{245} }{ 2 }\]

Answer 25

very good, now you can simplify a little bit further

what are factors of 245?

Answer 26

\[7\sqrt{5}\]

Answer 27

@unkleRhaukus
Please tell how you did the colours and brackets and notes etc. in your earlier explanation...

Answer 28

So you still didn't get the answer ???

Answer 29

Nope...

Answer 30

If multiplied, u gotta use FOIL
(x-8) (x+7) = 5
x^2 + 7x -8x -56 = 5
x^2 - x -56 = 5
x^2 - x -61 = 0
now solve x using quadratic equation

Answer 31

So u get 2 possible answers for x for this both are correct
x = -7.33
x = 8.33

Answer 32

awwww, thank yooooou !

Answer 33

UnkleRhaukus clearly explained that .. lol

Answer 34

And np if i understand something i'll help

Answer 35

lol, yea, i just didnt feel like doing it lol