Solve the following simultaneous equations:
2x - 3y = 3
4x² - 9y² = 3
Answers
Step-by-step explanation:
Answer
(i)


⇒ 4x + 3y = 48 eq.[1]


⇒ 2x - 3y = 4 eq.[2]
Adding eq.[1] and eq.[2], we get
⇒ 4x + 3y + 2x - 3y = 48 + 4
⇒ 6x = 52

Using this in eq.[1], we have


⇒ 104 + 9y = 144
⇒ 9y = 40

(ii)


⇒ x + 15y = 39
⇒ x = 39 - 15y eq.[1]


⇒ 4x + y = 38
Using eq.[1], we have
⇒ 4(39 - 15y) + y = 38
⇒ 156 - 60y + y = 38
⇒ 59y = 118
⇒ y = 2
Putting this value in eq.[2]
⇒ x = 39 - 15(2)
⇒ x = 39 - 30
⇒ x = 9
(iii)


⇒ 2y + 3x = 13xy eq.[1]


⇒ 5y - 4x = -2xy eq.[2]
Multiplying eq.[1] by 4 both side, and Multiplying eq.[2] by 3 both side, we get
8y + 12x = 52xy eq.[3]
15y - 12x = -6xy eq.[4]
Adding eq.[3] and eq.[4]
⇒ 8y + 12x + 15y - 12x = 52xy - 6xy
⇒ 23y = 46xy
⇒ 1 = 2x
2x+3y=8 and xy=2,
formula,
(a+b)
2
=a
2
+b
2
+2ab
∴(2x+3y)
2
=4x
2
+9y
2
+2(2x)(3y)
(2x+3y)
2
=4x
2
+9y
2
+12xy
8
2
=4x
2
+9y
2
+12(2)
∴4x
2
+9y
2
=64−24=40