The value of ab if 3a + 5b = 15 and 9a2 + 25b² = 75 is : 1. 4 2. 5 3. 6 4. 8

Given, 3a + 5b = 15 and 9a2 + 25b2 = 75 ⇒ (3a + 5b)2 = (3a)2 + (5b)2 + 2 × (3a) × (5b) ⇒ (3a + 5b)2 = 9a2 + 25b2 + 30ab ⇒ 152 = 75 + 30ab ⇒ 225 = 75 + 30ab ⇒ 30ab = 225 - 75 ⇒ 30ab = 150 ⇒ ab = ⇒ ab = 5. Hence, Option 2 is the correct option.

2.51 × 2.51 + 1.31 × 1.31 − 2.62 × 2.51 =
1.44
0.44
1
0

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If l + m − n = 9 and l² + m² + n² = 31, then mn + nl − lm is :
-25
25
-2
-5

View Answer Bookmark Now

If a − b + c = 6 and a² + b² + c² = 38, then ab + bc − ca is :
0
1
-1
not possible

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Mathematics

The value of ab if 3a + 5b = 15 and 9a² + 25b² = 75 is :
4
5
6
8

Expansions

Related Questions

2.51 × 2.51 + 1.31 × 1.31 − 2.62 × 2.51 =
1.44
0.44
1
0

If l + m − n = 9 and l² + m² + n² = 31, then mn + nl − lm is :
-25
25
-2
-5

If a − b + c = 6 and a² + b² + c² = 38, then ab + bc − ca is :
0
1
-1
not possible

Mathematics

The value of ab if 3a + 5b = 15 and 9a2 + 25b2 = 75 is :4568

Expansions

Related Questions

2.51 × 2.51 + 1.31 × 1.31 − 2.62 × 2.51 =1.440.4410

If l + m − n = 9 and l2 + m2 + n2 = 31, then mn + nl − lm is :-2525-2-5

If a − b + c = 6 and a2 + b2 + c2 = 38, then ab + bc − ca is :01-1not possible

The value of ab if 3a + 5b = 15 and 9a² + 25b² = 75 is :
4
5
6
8

2.51 × 2.51 + 1.31 × 1.31 − 2.62 × 2.51 =
1.44
0.44
1
0

If l + m − n = 9 and l² + m² + n² = 31, then mn + nl − lm is :
-25
25
-2
-5

If a − b + c = 6 and a² + b² + c² = 38, then ab + bc − ca is :
0
1
-1
not possible