Ax + By =5
Ax²+ By = 10
AX + By =50
AX + By = 130
13(x + y - xy) = 120(ATB)=?
Answers
Required Answer:-
Given:
- ax + by = 5
- ax² + by = 19
- ax³ + by³ = 50
- ax⁴ + by⁴ = 130
To find:
- The value of 13(x + y - xy) - 120(a + b)
Solution:
We have,
➡ ax + by = 5 ......(i)
➡ ax² + by² = 10 ......(ii)
➡ ax³ + by³ = 50 .......(iii)
➡ ax⁴ + by⁴ = 130 ........(iv)
To solve this question, we have to find out the values of the following.
- x + y = ?
- xy = ?
- a + b = ?
★ Let's start solving.
Multiplying both sides of equation (ii) by (x + y), we get,
➡ (ax² + by²)(x + y) = 10(x + y)
➡ ax³ + ax²y + bxy² + by³ = 10(x + y)
➡ ax³ + by³ + xy(ax + by) = 10(x + y)
Substituting the values of ax³ + by³ and ax + by, we get,
➡ 50 + 5xy = 10(x + y) .......(v)
Again,
Multiplying both sides of equation (iii) by (x + y), we get,
➡ (ax³ + by³)(x + y) = 50(x + y)
➡ ax⁴ + by⁴ + ax³y + bxy³ = 50(x + y)
➡ ax⁴ + by⁴ + xy(ax² + by²) = 50(x + y)
Again, substituting the values, we get,
➡ 130 + 100xy = 50(x + y) .......(vi)
Multiplying equation (v) by 2, we get,
➡ 100 + 100xy = 20(x + y) .......(vii)
Subtracting (vii) from (vi), we get,
➡ 30 = 30(x + y)
➡ x + y = 1 (★ Remember this)
Substituting the value of x + y in equation (v), we get,
➡ 50 + 5xy = 10
➡ 5xy = -40
➡ xy = -8 (★ Remember this)
Now, multiply both sides of equation (i) by (x + y). We get,
➡ (ax + by)(x + y) = 5(x + y)
➡ ax² + by² + axy + byx = 5(x + y)
Substitute all the values.
➡ 10 + xy(a + b) = 5
➡ -8(a + b) = -5
➡ (a + b) = -5/-8
➡ a + b = 5/8 (★ Remember this)
Thus,
13(x + y - xy) - 120(a + b)
= 13(1 - (-8)) - 120 × ⅝
= 13 × 9 - 75
= 117 - 75
= 42
Hence,
★ The value of 13(x + y - xy) - 120(a + b) is 42.
Answer:
- 13(x + y - xy) - 120(a + b) = 42.
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