7.) Зу = 2-х
2y + 10 = 6x

By cross multiplication method

x=

(a

1

b

2

−a

2

b

1

)

(b

1

c

2

−b

2

c

1

)

&

y=

(a

1

b

2

−a

2

b

1

)

(c

1

a

2

−c

2

a

1

)

Where a

1

x+b

1

y+c

1

=0 & a

2

x+b

2

y+c

2

=0

are 2 lines

⇒x=

2(−2)−(3×3)

3(−6)−(−2)(−17)

=

−13

−52

=4

y=

2(−2)−(3×3)

(−17)3−(−6)2

=

−13

−39

=3

⇒

x=4&y=3

a4 - 3a2 - 1

step-by-step explanation:

step   1   :

equation at the end of step   1   :

  ((a4) -   3a2) -   1

step   2   :

trying to factor by splitting the middle term

2.1     factoring   a4-3a2-1  

the first term is,   a4   its coefficient is   1 .

the middle term is,   -3a2   its coefficient is   -3 .

the last term, "the constant", is   -1