Question

Find the solution to the following system by substitution

y=-2x - 3
y=3x+12
A.(-3,-9)
B(-9/5,3/5)
C(3,21)
D(-3,3)

Answer 1

D(-3,3)

Explanation:

Solution Given:

y=-2x-3 ......equation 1.

y=3x+12 .......equation 2.

In substitution method we need to replace the value or put the value

Here substituting value of y of equation 1 in equation 2.

we get new equation

-2x-3=3x+12

adding 2x and 3 on both side,

-2x-3+2x+3=3x+12+2x+3

solving it

0= 5x+15

subtracting 15 on both side,

-15=5x+15-15

-15=5x

diving both side 5

-15/5=5x/5

-3=x

so value of x is -3

again substituting value of x in equation 1.

y=-2*-3-3=6-3=3

here -*-=+

so

(x,y)=(-3,3)