Q7 of 23 Page 87

For what value of x will l1 and l2 be parallel lines.

i.


ii.

(i) Given: l1||l2


∠1 = (2x + 20)° and ∠2 = (3x-10)°


∵ Corresponding angles are equal


∴ ∠1 = ∠2


⇒ (2x + 20)° = (3x-10)°


⇒ x = 30°


ii. Given: l1||l2


∠1 = (2x)° and ∠2 = (3x + 20)°


∵ Co-interior angles are supplementary


∴ ∠1 + ∠2 = 180°


⇒ (2x)° + (3x + 20)° = 180°


⇒ 5x = 160°


⇒ x = 32°


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