Linear Systems in Two Variables with applications. solve using elimination or substitution.

4x + 3/4y = 14
-9x+ 5/8y = -13

Question

Linear Systems in Two Variables with applications.  solve using elimination or substitution.

4x + 3/4y = 14
-9x+ 5/8y = -13

anonymous · Answer

Do you have an idea on what would be easier to use, elimination or substitution?

anonymous · Answer

not really... i know elimination mostly.

anonymous · Answer

Alright, well lets go with elimination then. (For this case it appears to be the easier way to solve it)

anonymous · Answer

What variable do you want to get rid of first?

jennychan12 · Answer

$$4x+\frac{ 3y }{ 4 } = 14$$
$$-9x +\frac{ 5y }{ 8 } = -13$$

to make it easier, multiply each equation by the denominator
$$16x+ 3y  = 56 $$ call this equation 1
$$-72x +5y = -104$$ call this equation 2
the next few steps requires algebra.

ELIMINATION
multiply equation 1 by -5 and equation 2 by 3

$$-80x- 15y  = -280 $$ 
$$-216x +15y = -312$$ 
add
$$-296x = 592 $$
$$x =  2 $$
plug this back into either equation 1 or 2

I'll choose equation 1.
$$16(2)+ 3y  = 56  $$
$$y=3$$

anonymous · Answer

that is perfect.. thank you so much, i didn't realize i could mulitply everything by the denominator.

jennychan12 · Answer

yeah, sometimes, you just hafta learn certain tricks to stuff. cuz you could've done it with fractions, but those are a nightmare....