What are the solutions of the following system?
x^2+y^2=25
2x+y=-5
A. (0, –5) and (–5, 5)
B.(0, –5) and (5, –15)
C.(0, –5) and (–4, 3)
D.(0, –5) and (4, –13)

Respuesta :

so what you do is solve for y in 2nd equation
minus 2x boh sides

y=-2x-5
sub that for y in other equation

x^2+(-2x-5)^2=25
x^2+4x^2+20x+25=25
5x^2+20x+25=25
mminus 25 both sides
5x^2+20x=0
factor
(x)(5x+20)=0
set to zero
x=0
5x+20=0
5x=-20
x=-4

sub back

y=-2x-5
y=-2(0)-5
y=-5
a point is (0,-5)
y=-2x-5
y=-2(-4)-5
y=-8-5
y=-13
another is (-4,-13)


(0,-5) and (-4,13)

I think it is C, but you forgot to put that 1 infront of the 3


Answer:

Option C is correct

the solution for the given system of equation is, (0, -5) and (-4, 3)

Step-by-step explanation:

Using identity:

[tex](a+b)^2=a^2+b^2+2ab[/tex]

Given the equation:

[tex]x^2+y^2=25[/tex]        .....[1]

[tex]2x+y=-5[/tex]               .....[2]

We can write [2] as:

[tex]y = -5-2x[/tex]

Substitute this in [1] we have;

[tex]x^2+(-5-2x)^2=25[/tex]

Using identity rule;

[tex]x^2+25+4x^2+20x = 25[/tex]

Combine like terms;

[tex]5x^2+20x+25 = 25[/tex]

Subtract 25 from both sides we have;

[tex]5x^2+20x=0[/tex]

⇒[tex]5x(x+4)=0[/tex]

By zero product property we have;

x = 0 and x+4 = 0

x = 0 and x = -4

Substitute these in [2] we have;

for x = 0

2(0)+y = -5

⇒[tex]y = -5[/tex]

For x = -4 ,

[tex]2(-4)+y = -5[/tex]

-8+y = -5

add 8 to both sides we have;

y = 3

Therefore, the solution for the given system of equation is, (0, -5) and (-4, 3)

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