how to multiply 15=a+2d by 25= 2a+9d please anwer just now as my test is tomoorow - Maths - Arithmetic Progressions

Question

how to multiply 15=a+2d by 25= 2a+9d please anwer just now as my
test is tomoorow

ramandeep.singh · Accepted Answer

Given the equations $15 = a + 2 d (1) 25 = a + 9 d (2)$ If we want to calculate the values of a and d, then we can eliminate any of a or d and calculate the other In this case, multiply equation (1) by 2, so that the coefficients of a become equal $30 = 2 a + 4 d (3)$ Subtracting equation (2) from (3), we get $5 = - 5 d ∴ d = - 1$ Substitute the value of d in equation (1) $15 = a + 2 (- 1) ∴ a = 17$ Thus, we get $a = 17 d = - 1$