hi guys!i need help! math crisis here please.....?

Question

i need help please.......can u answer these problems for me 3x^2+7x=20.....and t(2t+9)=-7......and 14(x-4)-(x+2)=(x+2)(x-4)
PS.....please explain how did u came up eith this answers...(please show your work).......thanks:)

Answer 1

(BTW, Jameswalrus is wrong on the first one)
Gollee these are tough! But they all break down to the quadratic equation. Watch!

3x^2 + 7x =20
Use quadratic equation to solve for x:

where x = -b +/- sqrt(b^2-4ac)/2a
a = 3, b=7, c=(-20)
so:
-7 +/- sqrt (7^2-4(3)(-20)/2(3)
(-7+/- 17)/6
x=-4, or 5/3. Eh?

t(2t+9)=-7
2t^2+9t+7=0
Quadratic equation again. a=2, b=9 c=7.
t=(-9 +/- 5)/4 t= -14/4, or -1

14(x-4)-(x+2)=(x+2)(x-4)
14x-56-x-2=x^2-2x-8
x^2-15x+50=0
quadratic where a=1, b=-15, and c=48
x=(15 +/- sqrt(25))/2
x=5, or 10

Answer 2

3x^2+7x=20

3x^2+7x-20=0 (Add -20 to both sides)
(x+10)(x-3)=0 (factor)
x=-10 OR x=3 (add the opposite of the number on the right to both sides.)

t(2t+9)=-7
2t^2+9t=-7 (distribute)
2t^2+9t+7=0 (add 7 to both sides)
(2t+7 )(t +1 )=0 (factor)
2t=-7 t=-1
t=-3.5 OR t=-1

14(x-4)-(x-2)= (x+2)(x-4)
14x-56-x-2=x^2-2x-8 (distribute, use FOIL on the right)
13x-58=x^2-2x-8 (combine like terms)
0=x^2-15x+50 (add -13x and 58 to both sides)
(x-10) (x-5)=0
x=10 OR x=5

Hope that helped!

Answer 3

Do your own work, but the first two are just quadratics and use the quadratic formula to solve. The last one, just distribute and combine like terms. Hint: more than likely, the last one will be another quadratic.