Product property is the answer
The error is that -2 times -5 is 10 not -10. Then carry on from there because that error meant the rest is wrong as well.

Assuming the sum starts at

, the

th partial sum is


As

, you're left with simply 1.
Answer:
The value of x in centimeters is 22.5 cm
Step-by-step explanation:
The corresponding sides of the similar triangles are proportion which means have equal ratios
∵ Δ ABC is similar to Δ FGH
∵ AB and FG are corresponding sides
∵ BC and GH are corresponding sides
∵ AC and FH are corresponding sides
→ That means the ratios between them are equal
∴
=
= 
∵ AB = 6 cm and FG = 15 cm
∵ BC = 5 cm and GH = 12.5 cm
∵ AC = 9 cm and FH = x
→ Substitute them in the rule above to find x
∴
=
= 
→ By using cross multiplication with the 1st and 3rd ratios
∵ 6 × x = 15 × 9
∴ 6x = 135
→ Divide both sides by 6 to find x
∵
= 
∴ x = 22.5 cm
∴ The value of x in centimeters is 22.5 cm
<span> Simplifying
4x + 4y = 0
Solving
4x + 4y = 0
Solving for variable 'x'.
Move all terms containing x to the left, all other terms to the right.
Add '-4y' to each side of the equation.
4x + 4y + -4y = 0 + -4y
Combine like terms:
4y + -4y = 0
4x + 0 = 0 + -4y
4x = 0 + -4y
Remove the zero:
4x = -4y
Divide each side by '4'.
x = -1y
Simplifying
x = -1y</span>