Question

answer this mcq step by step​

Answer 1

Answer:

here is your answer 232

Answer 2

1. Given,

3x + 7y = 20

xy = 4

To find:

9x² + 49y²

Solution:

9x² + 49y²

= (3x)² + (7y)²

= (3x+7y)² - 2*3x*7y               [∴ a²- b² = (a + b²) - 2ab]

= 20² - 2*21xy

= 400 - 42xy

= 400 - 42*4

= 400 - 168

= 232

So, the answer is (b) 232.

2. $\frac{(0.1)^2+(0.01)^2}{0.0001} -1$

$= \frac{0.01+0.0001}{0.0001} -1$

$=\frac{0.0101}{0.0001} -1$

$=101-1\\=100$

So, (a) 100.

3.

$\\a+\frac{1}{a}=3 \\\\(a+\frac{1}{a})^2 =3^2\\\\a^2+(\frac{1}{a} )^2+2*a*\frac{1}{a}=9$

$a^2+\frac{1}{a^2}+2=9$

$a^2+\frac{1}{a^2} =9-2$

$a^2+\frac{1}{a^2}=7$

So, the answer is (c) 7.

4. (d) is the answer.

CHECK :-

$RHS: (x-\frac{1}{x})^2-2\\\\=x^2+\frac{1}{x^2}+2-2\\ \\=x^2+\frac{1}{x^2}$

$LHS:\ (x-\frac{1}{x})^2\\\\=x^2+\frac{1}{x^2}-2$

$LHS\is\ not\ equal\ to\ RHS.$

5. Given,

ab = 8

a + b = 6

To find:

a² + b²

Solution:

$a^2+b^2\\=(a+b)^2-2ab\\=6^2-2*8\\=36-16\\=20$

So, the answer is (c) 20.