How do you solve 2( 9- 2y ) = 21?

2 Answers
Jan 3, 2018

y=(-3)/4

Explanation:

2(9-2y)=21

Let's start by using the distributive property

(2)(9)+(2)(-2y)=21

18 - 4y = 21

Then subtract color(red)(18) from both sides

cancel18 - 4y - cancelcolor(red)(18) = 21 - color(red)(18)

-4y = 3

Then finally, divide both sides by color(green)(-4)

(cancel(-4)y)/cancelcolor(green)(-4) = 3/color(green)(-4)

y=(-3)/4

Jan 3, 2018

Graphical Interpritation...

Explanation:

Graphical Approach

Since 2(9-2y) = 21

Both sides are equal to the same thing:

Let x = 2(9-2y) and x = 21

Now sketching each of the functions...

www.desmos.comwww.desmos.com

Now the solution to the question is were the interesection is, hence lieing on both lines, and satifying each equation

So in this case, solving for y;

color(blue)(y = -0.75 = -3/4